Initial commit

backend/venv/Lib/site-packages/pika/adapters/__init__.py

@@ -0,0 +1,23 @@
+"""
+Connection Adapters
+===================
+
+Pika provides multiple adapters to connect to RabbitMQ:
+
+- adapters.asyncio_connection.AsyncioConnection: Native Python3 AsyncIO use
+- adapters.blocking_connection.BlockingConnection: Enables blocking,
+  synchronous operation on top of library for simple uses.
+- adapters.gevent_connection.GeventConnection: Connection adapter for use with
+  Gevent.
+- adapters.select_connection.SelectConnection: A native event based connection
+  adapter that implements select, kqueue, poll and epoll.
+- adapters.tornado_connection.TornadoConnection: Connection adapter for use
+  with the Tornado web framework.
+- adapters.twisted_connection.TwistedProtocolConnection: Connection adapter for
+  use with the Twisted framework
+
+"""
+from pika.adapters.base_connection import BaseConnection
+from pika.adapters.blocking_connection import BlockingConnection
+from pika.adapters.select_connection import SelectConnection
+from pika.adapters.select_connection import IOLoop

backend/venv/Lib/site-packages/pika/adapters/asyncio_connection.py

@@ -0,0 +1,283 @@
+"""Use pika with the Asyncio EventLoop"""
+
+import asyncio
+import logging
+import sys
+
+from pika.adapters import base_connection
+from pika.adapters.utils import nbio_interface, io_services_utils
+
+LOGGER = logging.getLogger(__name__)
+
+
+if sys.platform == 'win32':
+    asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())
+
+
+class AsyncioConnection(base_connection.BaseConnection):
+    """ The AsyncioConnection runs on the Asyncio EventLoop.
+
+    """
+
+    def __init__(self,
+                 parameters=None,
+                 on_open_callback=None,
+                 on_open_error_callback=None,
+                 on_close_callback=None,
+                 custom_ioloop=None,
+                 internal_connection_workflow=True):
+        """ Create a new instance of the AsyncioConnection class, connecting
+        to RabbitMQ automatically
+
+        :param pika.connection.Parameters parameters: Connection parameters
+        :param callable on_open_callback: The method to call when the connection
+            is open
+        :param None | method on_open_error_callback: Called if the connection
+            can't be established or connection establishment is interrupted by
+            `Connection.close()`: on_open_error_callback(Connection, exception).
+        :param None | method on_close_callback: Called when a previously fully
+            open connection is closed:
+            `on_close_callback(Connection, exception)`, where `exception` is
+            either an instance of `exceptions.ConnectionClosed` if closed by
+            user or broker or exception of another type that describes the cause
+            of connection failure.
+        :param None | asyncio.AbstractEventLoop |
+            nbio_interface.AbstractIOServices custom_ioloop:
+                Defaults to asyncio.get_event_loop().
+        :param bool internal_connection_workflow: True for autonomous connection
+            establishment which is default; False for externally-managed
+            connection workflow via the `create_connection()` factory.
+
+        """
+        if isinstance(custom_ioloop, nbio_interface.AbstractIOServices):
+            nbio = custom_ioloop
+        else:
+            nbio = _AsyncioIOServicesAdapter(custom_ioloop)
+
+        super().__init__(
+            parameters,
+            on_open_callback,
+            on_open_error_callback,
+            on_close_callback,
+            nbio,
+            internal_connection_workflow=internal_connection_workflow)
+
+    @classmethod
+    def create_connection(cls,
+                          connection_configs,
+                          on_done,
+                          custom_ioloop=None,
+                          workflow=None):
+        """Implement
+        :py:classmethod::`pika.adapters.BaseConnection.create_connection()`.
+
+        """
+        nbio = _AsyncioIOServicesAdapter(custom_ioloop)
+
+        def connection_factory(params):
+            """Connection factory."""
+            if params is None:
+                raise ValueError('Expected pika.connection.Parameters '
+                                 'instance, but got None in params arg.')
+            return cls(
+                parameters=params,
+                custom_ioloop=nbio,
+                internal_connection_workflow=False)
+
+        return cls._start_connection_workflow(
+            connection_configs=connection_configs,
+            connection_factory=connection_factory,
+            nbio=nbio,
+            workflow=workflow,
+            on_done=on_done)
+
+
+class _AsyncioIOServicesAdapter(io_services_utils.SocketConnectionMixin,
+                                io_services_utils.StreamingConnectionMixin,
+                                nbio_interface.AbstractIOServices,
+                                nbio_interface.AbstractFileDescriptorServices):
+    """Implements
+    :py:class:`.utils.nbio_interface.AbstractIOServices` interface
+    on top of `asyncio`.
+
+    NOTE:
+    :py:class:`.utils.nbio_interface.AbstractFileDescriptorServices`
+    interface is only required by the mixins.
+
+    """
+
+    def __init__(self, loop=None):
+        """
+        :param asyncio.AbstractEventLoop | None loop: If None, gets default
+            event loop from asyncio.
+
+        """
+        self._loop = loop or asyncio.get_event_loop()
+
+    def get_native_ioloop(self):
+        """Implement
+        :py:meth:`.utils.nbio_interface.AbstractIOServices.get_native_ioloop()`.
+
+        """
+        return self._loop
+
+    def close(self):
+        """Implement
+        :py:meth:`.utils.nbio_interface.AbstractIOServices.close()`.
+
+        """
+        self._loop.close()
+
+    def run(self):
+        """Implement :py:meth:`.utils.nbio_interface.AbstractIOServices.run()`.
+
+        """
+        self._loop.run_forever()
+
+    def stop(self):
+        """Implement :py:meth:`.utils.nbio_interface.AbstractIOServices.stop()`.
+
+        """
+        self._loop.stop()
+
+    def add_callback_threadsafe(self, callback):
+        """Implement
+        :py:meth:`.utils.nbio_interface.AbstractIOServices.add_callback_threadsafe()`.
+
+        """
+        self._loop.call_soon_threadsafe(callback)
+
+    def call_later(self, delay, callback):
+        """Implement
+        :py:meth:`.utils.nbio_interface.AbstractIOServices.call_later()`.
+
+        """
+        return _TimerHandle(self._loop.call_later(delay, callback))
+
+    def getaddrinfo(self,
+                    host,
+                    port,
+                    on_done,
+                    family=0,
+                    socktype=0,
+                    proto=0,
+                    flags=0):
+        """Implement
+        :py:meth:`.utils.nbio_interface.AbstractIOServices.getaddrinfo()`.
+
+        """
+        return self._schedule_and_wrap_in_io_ref(
+            self._loop.getaddrinfo(
+                host,
+                port,
+                family=family,
+                type=socktype,
+                proto=proto,
+                flags=flags), on_done)
+
+    def set_reader(self, fd, on_readable):
+        """Implement
+        :py:meth:`.utils.nbio_interface.AbstractFileDescriptorServices.set_reader()`.
+
+        """
+        self._loop.add_reader(fd, on_readable)
+        LOGGER.debug('set_reader(%s, _)', fd)
+
+    def remove_reader(self, fd):
+        """Implement
+        :py:meth:`.utils.nbio_interface.AbstractFileDescriptorServices.remove_reader()`.
+
+        """
+        LOGGER.debug('remove_reader(%s)', fd)
+        return self._loop.remove_reader(fd)
+
+    def set_writer(self, fd, on_writable):
+        """Implement
+        :py:meth:`.utils.nbio_interface.AbstractFileDescriptorServices.set_writer()`.
+
+        """
+        self._loop.add_writer(fd, on_writable)
+        LOGGER.debug('set_writer(%s, _)', fd)
+
+    def remove_writer(self, fd):
+        """Implement
+        :py:meth:`.utils.nbio_interface.AbstractFileDescriptorServices.remove_writer()`.
+
+        """
+        LOGGER.debug('remove_writer(%s)', fd)
+        return self._loop.remove_writer(fd)
+
+    def _schedule_and_wrap_in_io_ref(self, coro, on_done):
+        """Schedule the coroutine to run and return _AsyncioIOReference
+
+        :param coroutine-obj coro:
+        :param callable on_done: user callback that takes the completion result
+            or exception as its only arg. It will not be called if the operation
+            was cancelled.
+        :rtype: _AsyncioIOReference which is derived from
+            nbio_interface.AbstractIOReference
+
+        """
+        if not callable(on_done):
+            raise TypeError(
+                'on_done arg must be callable, but got {!r}'.format(on_done))
+
+        return _AsyncioIOReference(
+            asyncio.ensure_future(coro, loop=self._loop), on_done)
+
+
+class _TimerHandle(nbio_interface.AbstractTimerReference):
+    """This module's adaptation of `nbio_interface.AbstractTimerReference`.
+
+    """
+
+    def __init__(self, handle):
+        """
+
+        :param asyncio.Handle handle:
+        """
+        self._handle = handle
+
+    def cancel(self):
+        if self._handle is not None:
+            self._handle.cancel()
+            self._handle = None
+
+
+class _AsyncioIOReference(nbio_interface.AbstractIOReference):
+    """This module's adaptation of `nbio_interface.AbstractIOReference`.
+
+    """
+
+    def __init__(self, future, on_done):
+        """
+        :param asyncio.Future future:
+        :param callable on_done: user callback that takes the completion result
+            or exception as its only arg. It will not be called if the operation
+            was cancelled.
+
+        """
+        if not callable(on_done):
+            raise TypeError(
+                'on_done arg must be callable, but got {!r}'.format(on_done))
+
+        self._future = future
+
+        def on_done_adapter(future):
+            """Handle completion callback from the future instance"""
+
+            # NOTE: Asyncio schedules callback for cancelled futures, but pika
+            # doesn't want that
+            if not future.cancelled():
+                on_done(future.exception() or future.result())
+
+        future.add_done_callback(on_done_adapter)
+
+    def cancel(self):
+        """Cancel pending operation
+
+        :returns: False if was already done or cancelled; True otherwise
+        :rtype: bool
+
+        """
+        return self._future.cancel()

backend/venv/Lib/site-packages/pika/adapters/base_connection.py

@@ -0,0 +1,501 @@
+"""Base class extended by connection adapters. This extends the
+connection.Connection class to encapsulate connection behavior but still
+isolate socket and low level communication.
+
+"""
+import abc
+import functools
+import logging
+
+import pika.compat
+import pika.exceptions
+import pika.tcp_socket_opts
+
+from pika.adapters.utils import connection_workflow, nbio_interface
+from pika import connection
+
+LOGGER = logging.getLogger(__name__)
+
+
+class BaseConnection(connection.Connection):
+    """BaseConnection class that should be extended by connection adapters.
+
+    This class abstracts I/O loop and transport services from pika core.
+
+    """
+
+    def __init__(self, parameters, on_open_callback, on_open_error_callback,
+                 on_close_callback, nbio, internal_connection_workflow):
+        """Create a new instance of the Connection object.
+
+        :param None|pika.connection.Parameters parameters: Connection parameters
+        :param None|method on_open_callback: Method to call on connection open
+        :param None | method on_open_error_callback: Called if the connection
+            can't be established or connection establishment is interrupted by
+            `Connection.close()`: on_open_error_callback(Connection, exception).
+        :param None | method on_close_callback: Called when a previously fully
+            open connection is closed:
+            `on_close_callback(Connection, exception)`, where `exception` is
+            either an instance of `exceptions.ConnectionClosed` if closed by
+            user or broker or exception of another type that describes the cause
+            of connection failure.
+        :param pika.adapters.utils.nbio_interface.AbstractIOServices nbio:
+            asynchronous services
+        :param bool internal_connection_workflow: True for autonomous connection
+            establishment which is default; False for externally-managed
+            connection workflow via the `create_connection()` factory.
+        :raises: RuntimeError
+        :raises: ValueError
+
+        """
+        if parameters and not isinstance(parameters, connection.Parameters):
+            raise ValueError(
+                'Expected instance of Parameters, not %r' % (parameters,))
+
+        self._nbio = nbio
+
+        self._connection_workflow = None  # type: connection_workflow.AMQPConnectionWorkflow
+        self._transport = None  # type: pika.adapters.utils.nbio_interface.AbstractStreamTransport
+
+        self._got_eof = False  # transport indicated EOF (connection reset)
+
+        super(BaseConnection, self).__init__(
+            parameters,
+            on_open_callback,
+            on_open_error_callback,
+            on_close_callback,
+            internal_connection_workflow=internal_connection_workflow)
+
+    def _init_connection_state(self):
+        """Initialize or reset all of our internal state variables for a given
+        connection. If we disconnect and reconnect, all of our state needs to
+        be wiped.
+
+        """
+        super(BaseConnection, self)._init_connection_state()
+
+        self._connection_workflow = None
+        self._transport = None
+        self._got_eof = False
+
+    def __repr__(self):
+
+        # def get_socket_repr(sock):
+        #     """Return socket info suitable for use in repr"""
+        #     if sock is None:
+        #         return None
+        #
+        #     sockname = None
+        #     peername = None
+        #     try:
+        #         sockname = sock.getsockname()
+        #     except pika.compat.SOCKET_ERROR:
+        #         # closed?
+        #         pass
+        #     else:
+        #         try:
+        #             peername = sock.getpeername()
+        #         except pika.compat.SOCKET_ERROR:
+        #             # not connected?
+        #             pass
+        #
+        #     return '%s->%s' % (sockname, peername)
+        # TODO need helpful __repr__ in transports
+        return ('<%s %s transport=%s params=%s>' % (
+            self.__class__.__name__, self._STATE_NAMES[self.connection_state],
+            self._transport, self.params))
+
+    @classmethod
+    @abc.abstractmethod
+    def create_connection(cls,
+                          connection_configs,
+                          on_done,
+                          custom_ioloop=None,
+                          workflow=None):
+        """Asynchronously create a connection to an AMQP broker using the given
+        configurations. Will attempt to connect using each config in the given
+        order, including all compatible resolved IP addresses of the hostname
+        supplied in each config, until one is established or all attempts fail.
+
+        See also `_start_connection_workflow()`.
+
+        :param sequence connection_configs: A sequence of one or more
+            `pika.connection.Parameters`-based objects.
+        :param callable on_done: as defined in
+            `connection_workflow.AbstractAMQPConnectionWorkflow.start()`.
+        :param object | None custom_ioloop: Provide a custom I/O loop that is
+            native to the specific adapter implementation; if None, the adapter
+            will use a default loop instance, which is typically a singleton.
+        :param connection_workflow.AbstractAMQPConnectionWorkflow | None workflow:
+            Pass an instance of an implementation of the
+            `connection_workflow.AbstractAMQPConnectionWorkflow` interface;
+            defaults to a `connection_workflow.AMQPConnectionWorkflow` instance
+            with default values for optional args.
+        :returns: Connection workflow instance in use. The user should limit
+            their interaction with this object only to it's `abort()` method.
+        :rtype: connection_workflow.AbstractAMQPConnectionWorkflow
+
+        """
+        raise NotImplementedError
+
+    @classmethod
+    def _start_connection_workflow(cls, connection_configs, connection_factory,
+                                   nbio, workflow, on_done):
+        """Helper function for custom implementations of `create_connection()`.
+
+        :param sequence connection_configs: A sequence of one or more
+            `pika.connection.Parameters`-based objects.
+        :param callable connection_factory: A function that takes
+            `pika.connection.Parameters` as its only arg and returns a brand new
+            `pika.connection.Connection`-based adapter instance each time it is
+            called. The factory must instantiate the connection with
+            `internal_connection_workflow=False`.
+        :param pika.adapters.utils.nbio_interface.AbstractIOServices nbio:
+        :param connection_workflow.AbstractAMQPConnectionWorkflow | None workflow:
+            Pass an instance of an implementation of the
+            `connection_workflow.AbstractAMQPConnectionWorkflow` interface;
+            defaults to a `connection_workflow.AMQPConnectionWorkflow` instance
+            with default values for optional args.
+        :param callable on_done: as defined in
+            :py:meth:`connection_workflow.AbstractAMQPConnectionWorkflow.start()`.
+        :returns: Connection workflow instance in use. The user should limit
+            their interaction with this object only to it's `abort()` method.
+        :rtype: connection_workflow.AbstractAMQPConnectionWorkflow
+
+        """
+        if workflow is None:
+            workflow = connection_workflow.AMQPConnectionWorkflow()
+            LOGGER.debug('Created default connection workflow %r', workflow)
+
+        if isinstance(workflow, connection_workflow.AMQPConnectionWorkflow):
+            workflow.set_io_services(nbio)
+
+        def create_connector():
+            """`AMQPConnector` factory."""
+            return connection_workflow.AMQPConnector(
+                lambda params: _StreamingProtocolShim(
+                    connection_factory(params)),
+                nbio)
+
+        workflow.start(
+            connection_configs=connection_configs,
+            connector_factory=create_connector,
+            native_loop=nbio.get_native_ioloop(),
+            on_done=functools.partial(cls._unshim_connection_workflow_callback,
+                                      on_done))
+
+        return workflow
+
+    @property
+    def ioloop(self):
+        """
+        :returns: the native I/O loop instance underlying async services selected
+            by user or the default selected by the specialized connection
+            adapter (e.g., Twisted reactor, `asyncio.SelectorEventLoop`,
+            `select_connection.IOLoop`, etc.)
+        :rtype: object
+        """
+        return self._nbio.get_native_ioloop()
+
+    def _adapter_call_later(self, delay, callback):
+        """Implement
+        :py:meth:`pika.connection.Connection._adapter_call_later()`.
+
+        """
+        return self._nbio.call_later(delay, callback)
+
+    def _adapter_remove_timeout(self, timeout_id):
+        """Implement
+        :py:meth:`pika.connection.Connection._adapter_remove_timeout()`.
+
+        """
+        timeout_id.cancel()
+
+    def _adapter_add_callback_threadsafe(self, callback):
+        """Implement
+        :py:meth:`pika.connection.Connection._adapter_add_callback_threadsafe()`.
+
+        """
+        if not callable(callback):
+            raise TypeError(
+                'callback must be a callable, but got %r' % (callback,))
+
+        self._nbio.add_callback_threadsafe(callback)
+
+    def _adapter_connect_stream(self):
+        """Initiate full-stack connection establishment asynchronously for
+        internally-initiated connection bring-up.
+
+        Upon failed completion, we will invoke
+        `Connection._on_stream_terminated()`. NOTE: On success,
+        the stack will be up already, so there is no corresponding callback.
+
+        """
+        self._connection_workflow = connection_workflow.AMQPConnectionWorkflow(
+            _until_first_amqp_attempt=True)
+
+        self._connection_workflow.set_io_services(self._nbio)
+
+        def create_connector():
+            """`AMQPConnector` factory"""
+            return connection_workflow.AMQPConnector(
+                lambda _params: _StreamingProtocolShim(self), self._nbio)
+
+        self._connection_workflow.start(
+            [self.params],
+            connector_factory=create_connector,
+            native_loop=self._nbio.get_native_ioloop(),
+            on_done=functools.partial(self._unshim_connection_workflow_callback,
+                                      self._on_connection_workflow_done))
+
+    @staticmethod
+    def _unshim_connection_workflow_callback(user_on_done, shim_or_exc):
+        """
+
+        :param callable user_on_done: user's `on_done` callback as defined in
+            :py:meth:`connection_workflow.AbstractAMQPConnectionWorkflow.start()`.
+        :param _StreamingProtocolShim | Exception shim_or_exc:
+        """
+        result = shim_or_exc
+        if isinstance(result, _StreamingProtocolShim):
+            result = result.conn
+
+        user_on_done(result)
+
+    def _abort_connection_workflow(self):
+        """Asynchronously abort connection workflow. Upon
+        completion, `Connection._on_stream_terminated()` will be called with None
+        as the error argument.
+
+        Assumption: may be called only while connection is opening.
+
+        """
+        assert not self._opened, (
+            '_abort_connection_workflow() may be called only when '
+            'connection is opening.')
+
+        if self._transport is None:
+            # NOTE: this is possible only when user calls Connection.close() to
+            # interrupt internally-initiated connection establishment.
+            # self._connection_workflow.abort() would not call
+            # Connection.close() before pairing of connection with transport.
+            assert self._internal_connection_workflow, (
+                'Unexpected _abort_connection_workflow() call with '
+                'no transport in external connection workflow mode.')
+
+            # This will result in call to _on_connection_workflow_done() upon
+            # completion
+            self._connection_workflow.abort()
+        else:
+            # NOTE: we can't use self._connection_workflow.abort() in this case,
+            # because it would result in infinite recursion as we're called
+            # from Connection.close() and _connection_workflow.abort() calls
+            # Connection.close() to abort a connection that's already been
+            # paired with a transport. During internally-initiated connection
+            # establishment, AMQPConnectionWorkflow will discover that user
+            # aborted the connection when it receives
+            # pika.exceptions.ConnectionOpenAborted.
+
+            # This completes asynchronously, culminating in call to our method
+            # `connection_lost()`
+            self._transport.abort()
+
+    def _on_connection_workflow_done(self, conn_or_exc):
+        """`AMQPConnectionWorkflow` completion callback.
+
+        :param BaseConnection | Exception conn_or_exc: Our own connection
+            instance on success; exception on failure. See
+            `AbstractAMQPConnectionWorkflow.start()` for details.
+
+        """
+        LOGGER.debug('Full-stack connection workflow completed: %r',
+                     conn_or_exc)
+
+        self._connection_workflow = None
+
+        # Notify protocol of failure
+        if isinstance(conn_or_exc, Exception):
+            self._transport = None
+            if isinstance(conn_or_exc,
+                          connection_workflow.AMQPConnectionWorkflowAborted):
+                LOGGER.info('Full-stack connection workflow aborted: %r',
+                            conn_or_exc)
+                # So that _handle_connection_workflow_failure() will know it's
+                # not a failure
+                conn_or_exc = None
+            else:
+                LOGGER.error('Full-stack connection workflow failed: %r',
+                             conn_or_exc)
+                if (isinstance(conn_or_exc,
+                               connection_workflow.AMQPConnectionWorkflowFailed)
+                        and isinstance(
+                            conn_or_exc.exceptions[-1], connection_workflow.
+                            AMQPConnectorSocketConnectError)):
+                    conn_or_exc = pika.exceptions.AMQPConnectionError(
+                        conn_or_exc)
+
+            self._handle_connection_workflow_failure(conn_or_exc)
+        else:
+            # NOTE: On success, the stack will be up already, so there is no
+            #       corresponding callback.
+            assert conn_or_exc is self, \
+                'Expected self conn={!r} from workflow, but got {!r}.'.format(
+                    self, conn_or_exc)
+
+    def _handle_connection_workflow_failure(self, error):
+        """Handle failure of self-initiated stack bring-up and call
+        `Connection._on_stream_terminated()` if connection is not in closed state
+        yet. Called by adapter layer when the full-stack connection workflow
+        fails.
+
+        :param Exception | None error: exception instance describing the reason
+            for failure or None if the connection workflow was aborted.
+        """
+        if error is None:
+            LOGGER.info('Self-initiated stack bring-up aborted.')
+        else:
+            LOGGER.error('Self-initiated stack bring-up failed: %r', error)
+
+        if not self.is_closed:
+            self._on_stream_terminated(error)
+        else:
+            # This may happen when AMQP layer bring up was started but did not
+            # complete
+            LOGGER.debug('_handle_connection_workflow_failure(): '
+                         'suppressing - connection already closed.')
+
+    def _adapter_disconnect_stream(self):
+        """Asynchronously bring down the streaming transport layer and invoke
+        `Connection._on_stream_terminated()` asynchronously when complete.
+
+        """
+        if not self._opened:
+            self._abort_connection_workflow()
+        else:
+            # This completes asynchronously, culminating in call to our method
+            # `connection_lost()`
+            self._transport.abort()
+
+    def _adapter_emit_data(self, data):
+        """Take ownership of data and send it to AMQP server as soon as
+        possible.
+
+        :param bytes data:
+
+        """
+        self._transport.write(data)
+
+    def _proto_connection_made(self, transport):
+        """Introduces transport to protocol after transport is connected.
+
+        :py:class:`.utils.nbio_interface.AbstractStreamProtocol` implementation.
+
+        :param nbio_interface.AbstractStreamTransport transport:
+        :raises Exception: Exception-based exception on error
+
+        """
+        self._transport = transport
+
+        # Let connection know that stream is available
+        self._on_stream_connected()
+
+    def _proto_connection_lost(self, error):
+        """Called upon loss or closing of TCP connection.
+
+        :py:class:`.utils.nbio_interface.AbstractStreamProtocol` implementation.
+
+        NOTE: `connection_made()` and `connection_lost()` are each called just
+        once and in that order. All other callbacks are called between them.
+
+        :param BaseException | None error: An exception (check for
+            `BaseException`) indicates connection failure. None indicates that
+            connection was closed on this side, such as when it's aborted or
+            when `AbstractStreamProtocol.eof_received()` returns a falsy result.
+        :raises Exception: Exception-based exception on error
+
+        """
+        self._transport = None
+
+        if error is None:
+            # Either result of `eof_received()` or abort
+            if self._got_eof:
+                error = pika.exceptions.StreamLostError(
+                    'Transport indicated EOF')
+        else:
+            error = pika.exceptions.StreamLostError(
+                'Stream connection lost: {!r}'.format(error))
+
+        LOGGER.log(logging.DEBUG if error is None else logging.ERROR,
+                   'connection_lost: %r', error)
+
+        self._on_stream_terminated(error)
+
+    def _proto_eof_received(self):  # pylint: disable=R0201
+        """Called after the remote peer shuts its write end of the connection.
+        :py:class:`.utils.nbio_interface.AbstractStreamProtocol` implementation.
+
+        :returns: A falsy value (including None) will cause the transport to
+            close itself, resulting in an eventual `connection_lost()` call
+            from the transport. If a truthy value is returned, it will be the
+            protocol's responsibility to close/abort the transport.
+        :rtype: falsy|truthy
+        :raises Exception: Exception-based exception on error
+
+        """
+        LOGGER.error('Transport indicated EOF.')
+
+        self._got_eof = True
+
+        # This is how a reset connection will typically present itself
+        # when we have nothing to send to the server over plaintext stream.
+        #
+        # Have transport tear down the connection and invoke our
+        # `connection_lost` method
+        return False
+
+    def _proto_data_received(self, data):
+        """Called to deliver incoming data from the server to the protocol.
+
+        :py:class:`.utils.nbio_interface.AbstractStreamProtocol` implementation.
+
+        :param data: Non-empty data bytes.
+        :raises Exception: Exception-based exception on error
+
+        """
+        self._on_data_available(data)
+
+
+class _StreamingProtocolShim(nbio_interface.AbstractStreamProtocol):
+    """Shim for callbacks from transport so that we BaseConnection can
+    delegate to private methods, thus avoiding contamination of API with
+    methods that look public, but aren't.
+
+    """
+
+    # Override AbstractStreamProtocol abstract methods to enable instantiation
+    connection_made = None
+    connection_lost = None
+    eof_received = None
+    data_received = None
+
+    def __init__(self, conn):
+        """
+        :param BaseConnection conn:
+        """
+        self.conn = conn
+        # pylint: disable=W0212
+        self.connection_made = conn._proto_connection_made
+        self.connection_lost = conn._proto_connection_lost
+        self.eof_received = conn._proto_eof_received
+        self.data_received = conn._proto_data_received
+
+    def __getattr__(self, attr):
+        """Proxy inexistent attribute requests to our connection instance
+        so that AMQPConnectionWorkflow/AMQPConnector may treat the shim as an
+        actual connection.
+
+        """
+        return getattr(self.conn, attr)
+
+    def __repr__(self):
+        return '{}: {!r}'.format(self.__class__.__name__, self.conn)

backend/venv/Lib/site-packages/pika/adapters/gevent_connection.py

@@ -0,0 +1,469 @@
+"""Use pika with the Gevent IOLoop."""
+
+import functools
+import logging
+import os
+import threading
+import weakref
+
+try:
+    import queue
+except ImportError:  # Python <= v2.7
+    import Queue as queue
+
+import gevent
+import gevent.hub
+import gevent.socket
+
+import pika.compat
+from pika.adapters.base_connection import BaseConnection
+from pika.adapters.utils.io_services_utils import check_callback_arg
+from pika.adapters.utils.nbio_interface import (
+    AbstractIOReference,
+    AbstractIOServices,
+)
+from pika.adapters.utils.selector_ioloop_adapter import (
+    AbstractSelectorIOLoop,
+    SelectorIOServicesAdapter,
+)
+
+LOGGER = logging.getLogger(__name__)
+
+
+class GeventConnection(BaseConnection):
+    """Implementation of pika's ``BaseConnection``.
+
+    An async selector-based connection which integrates with Gevent.
+    """
+
+    def __init__(self,
+                 parameters=None,
+                 on_open_callback=None,
+                 on_open_error_callback=None,
+                 on_close_callback=None,
+                 custom_ioloop=None,
+                 internal_connection_workflow=True):
+        """Create a new GeventConnection instance and connect to RabbitMQ on
+        Gevent's event-loop.
+
+        :param pika.connection.Parameters|None parameters: The connection
+            parameters
+        :param callable|None on_open_callback: The method to call when the
+            connection is open
+        :param callable|None on_open_error_callback: Called if the connection
+            can't be established or connection establishment is interrupted by
+            `Connection.close()`:
+            on_open_error_callback(Connection, exception)
+        :param callable|None on_close_callback: Called when a previously fully
+            open connection is closed:
+            `on_close_callback(Connection, exception)`, where `exception` is
+            either an instance of `exceptions.ConnectionClosed` if closed by
+            user or broker or exception of another type that describes the
+            cause of connection failure
+        :param gevent._interfaces.ILoop|nbio_interface.AbstractIOServices|None
+            custom_ioloop: Use a custom Gevent ILoop.
+        :param bool internal_connection_workflow: True for autonomous connection
+            establishment which is default; False for externally-managed
+            connection workflow via the `create_connection()` factory
+        """
+        if pika.compat.ON_WINDOWS:
+            raise RuntimeError('GeventConnection is not supported on Windows.')
+
+        custom_ioloop = (custom_ioloop or
+                         _GeventSelectorIOLoop(gevent.get_hub()))
+
+        if isinstance(custom_ioloop, AbstractIOServices):
+            nbio = custom_ioloop
+        else:
+            nbio = _GeventSelectorIOServicesAdapter(custom_ioloop)
+
+        super(GeventConnection, self).__init__(
+            parameters,
+            on_open_callback,
+            on_open_error_callback,
+            on_close_callback,
+            nbio,
+            internal_connection_workflow=internal_connection_workflow)
+
+    @classmethod
+    def create_connection(cls,
+                          connection_configs,
+                          on_done,
+                          custom_ioloop=None,
+                          workflow=None):
+        """Implement
+        :py:classmethod::`pika.adapters.BaseConnection.create_connection()`.
+        """
+        custom_ioloop = (custom_ioloop or
+                         _GeventSelectorIOLoop(gevent.get_hub()))
+
+        nbio = _GeventSelectorIOServicesAdapter(custom_ioloop)
+
+        def connection_factory(params):
+            """Connection factory."""
+            if params is None:
+                raise ValueError('Expected pika.connection.Parameters '
+                                 'instance, but got None in params arg.')
+            return cls(parameters=params,
+                       custom_ioloop=nbio,
+                       internal_connection_workflow=False)
+
+        return cls._start_connection_workflow(
+            connection_configs=connection_configs,
+            connection_factory=connection_factory,
+            nbio=nbio,
+            workflow=workflow,
+            on_done=on_done)
+
+
+class _TSafeCallbackQueue(object):
+    """Dispatch callbacks from any thread to be executed in the main thread
+    efficiently with IO events.
+    """
+
+    def __init__(self):
+        """
+        :param _GeventSelectorIOLoop loop: IO loop to add callbacks to.
+        """
+        # Thread-safe, blocking queue.
+        self._queue = queue.Queue()
+        # PIPE to trigger an event when the queue is ready.
+        self._read_fd, self._write_fd = os.pipe()
+        # Lock around writes to the PIPE in case some platform/implementation
+        # requires this.
+        self._write_lock = threading.RLock()
+
+    @property
+    def fd(self):
+        """The file-descriptor to register for READ events in the IO loop."""
+        return self._read_fd
+
+    def add_callback_threadsafe(self, callback):
+        """Add an item to the queue from any thread. The configured handler
+        will be invoked with the item in the main thread.
+
+        :param item: Object to add to the queue.
+        """
+        self._queue.put(callback)
+        with self._write_lock:
+            # The value written is not important.
+            os.write(self._write_fd, b'\xFF')
+
+    def run_next_callback(self):
+        """Invoke the next callback from the queue.
+
+        MUST run in the main thread. If no callback was added to the queue,
+        this will block the IO loop.
+
+        Performs a blocking READ on the pipe so must only be called when the
+        pipe is ready for reading.
+        """
+        try:
+            callback = self._queue.get_nowait()
+        except queue.Empty:
+            # Should never happen.
+            LOGGER.warning("Callback queue was empty.")
+        else:
+            # Read the byte from the pipe so the event doesn't re-fire.
+            os.read(self._read_fd, 1)
+            callback()
+
+
+class _GeventSelectorIOLoop(AbstractSelectorIOLoop):
+    """Implementation of `AbstractSelectorIOLoop` using the Gevent event loop.
+
+    Required by implementations of `SelectorIOServicesAdapter`.
+    """
+    # Gevent's READ and WRITE masks are defined as 1 and 2 respectively. No
+    # ERROR mask is defined.
+    # See http://www.gevent.org/api/gevent.hub.html#gevent._interfaces.ILoop.io
+    READ = 1
+    WRITE = 2
+    ERROR = 0
+
+    def __init__(self, gevent_hub=None):
+        """
+        :param gevent._interfaces.ILoop gevent_loop:
+        """
+        self._hub = gevent_hub or gevent.get_hub()
+        self._io_watchers_by_fd = {}
+        # Used to start/stop the loop.
+        self._waiter = gevent.hub.Waiter()
+
+        # For adding callbacks from other threads. See `add_callback(..)`.
+        self._callback_queue = _TSafeCallbackQueue()
+
+        def run_callback_in_main_thread(fd, events):
+            """Swallow the fd and events arguments."""
+            del fd
+            del events
+            self._callback_queue.run_next_callback()
+
+        self.add_handler(self._callback_queue.fd, run_callback_in_main_thread,
+                         self.READ)
+
+    def close(self):
+        """Release the loop's resources."""
+        self._hub.loop.destroy()
+        self._hub = None
+
+    def start(self):
+        """Run the I/O loop. It will loop until requested to exit. See `stop()`.
+        """
+        LOGGER.debug("Passing control to Gevent's IOLoop")
+        self._waiter.get()  # Block until 'stop()' is called.
+
+        LOGGER.debug("Control was passed back from Gevent's IOLoop")
+        self._waiter.clear()
+
+    def stop(self):
+        """Request exit from the ioloop. The loop is NOT guaranteed to
+        stop before this method returns.
+
+        To invoke `stop()` safely from a thread other than this IOLoop's thread,
+        call it via `add_callback_threadsafe`; e.g.,
+
+            `ioloop.add_callback(ioloop.stop)`
+        """
+        self._waiter.switch(None)
+
+    def add_callback(self, callback):
+        """Requests a call to the given function as soon as possible in the
+        context of this IOLoop's thread.
+
+        NOTE: This is the only thread-safe method in IOLoop. All other
+        manipulations of IOLoop must be performed from the IOLoop's thread.
+
+        For example, a thread may request a call to the `stop` method of an
+        ioloop that is running in a different thread via
+        `ioloop.add_callback_threadsafe(ioloop.stop)`
+
+        :param callable callback: The callback method
+        """
+        if gevent.get_hub() == self._hub:
+            # We're in the main thread; just add the callback.
+            LOGGER.debug("Adding callback from main thread")
+            self._hub.loop.run_callback(callback)
+        else:
+            # This isn't the main thread and Gevent's hub/loop don't provide
+            # any thread-safety so enqueue the callback for it to be registered
+            # in the main thread.
+            LOGGER.debug("Adding callback from another thread")
+            callback = functools.partial(self._hub.loop.run_callback, callback)
+            self._callback_queue.add_callback_threadsafe(callback)
+
+    def call_later(self, delay, callback):
+        """Add the callback to the IOLoop timer to be called after delay seconds
+        from the time of call on best-effort basis. Returns a handle to the
+        timeout.
+
+        :param float delay: The number of seconds to wait to call callback
+        :param callable callback: The callback method
+        :returns: handle to the created timeout that may be passed to
+            `remove_timeout()`
+        :rtype: object
+        """
+        timer = self._hub.loop.timer(delay)
+        timer.start(callback)
+        return timer
+
+    def remove_timeout(self, timeout_handle):
+        """Remove a timeout
+
+        :param timeout_handle: Handle of timeout to remove
+        """
+        timeout_handle.close()
+
+    def add_handler(self, fd, handler, events):
+        """Start watching the given file descriptor for events
+
+        :param int fd: The file descriptor
+        :param callable handler: When requested event(s) occur,
+            `handler(fd, events)` will be called.
+        :param int events: The event mask (READ|WRITE)
+        """
+        io_watcher = self._hub.loop.io(fd, events)
+        self._io_watchers_by_fd[fd] = io_watcher
+        io_watcher.start(handler, fd, events)
+
+    def update_handler(self, fd, events):
+        """Change the events being watched for.
+
+        :param int fd: The file descriptor
+        :param int events: The new event mask (READ|WRITE)
+        """
+        io_watcher = self._io_watchers_by_fd[fd]
+        # Save callback from the original watcher. The close the old watcher
+        # and create a new one using the saved callback and the new events.
+        callback = io_watcher.callback
+        io_watcher.close()
+        del self._io_watchers_by_fd[fd]
+        self.add_handler(fd, callback, events)
+
+    def remove_handler(self, fd):
+        """Stop watching the given file descriptor for events
+
+        :param int fd: The file descriptor
+        """
+        io_watcher = self._io_watchers_by_fd[fd]
+        io_watcher.close()
+        del self._io_watchers_by_fd[fd]
+
+
+class _GeventSelectorIOServicesAdapter(SelectorIOServicesAdapter):
+    """SelectorIOServicesAdapter implementation using Gevent's DNS resolver."""
+
+    def getaddrinfo(self,
+                    host,
+                    port,
+                    on_done,
+                    family=0,
+                    socktype=0,
+                    proto=0,
+                    flags=0):
+        """Implement :py:meth:`.nbio_interface.AbstractIOServices.getaddrinfo()`.
+        """
+        resolver = _GeventAddressResolver(native_loop=self._loop,
+                                          host=host,
+                                          port=port,
+                                          family=family,
+                                          socktype=socktype,
+                                          proto=proto,
+                                          flags=flags,
+                                          on_done=on_done)
+        resolver.start()
+        # Return needs an implementation of `AbstractIOReference`.
+        return _GeventIOLoopIOHandle(resolver)
+
+
+class _GeventIOLoopIOHandle(AbstractIOReference):
+    """Implement `AbstractIOReference`.
+
+    Only used to wrap the _GeventAddressResolver.
+    """
+
+    def __init__(self, subject):
+        """
+        :param subject: subject of the reference containing a `cancel()` method
+        """
+        self._cancel = subject.cancel
+
+    def cancel(self):
+        """Cancel pending operation
+
+        :returns: False if was already done or cancelled; True otherwise
+        :rtype: bool
+        """
+        return self._cancel()
+
+
+class _GeventAddressResolver(object):
+    """Performs getaddrinfo asynchronously Gevent's configured resolver in a
+    separate greenlet and invoking the provided callback with the result.
+
+    See: http://www.gevent.org/dns.html
+    """
+    __slots__ = (
+        '_loop',
+        '_on_done',
+        '_greenlet',
+        # getaddrinfo(..) args:
+        '_ga_host',
+        '_ga_port',
+        '_ga_family',
+        '_ga_socktype',
+        '_ga_proto',
+        '_ga_flags')
+
+    def __init__(self, native_loop, host, port, family, socktype, proto, flags,
+                 on_done):
+        """Initialize the `_GeventAddressResolver`.
+
+        :param AbstractSelectorIOLoop native_loop:
+        :param host: `see socket.getaddrinfo()`
+        :param port: `see socket.getaddrinfo()`
+        :param family: `see socket.getaddrinfo()`
+        :param socktype: `see socket.getaddrinfo()`
+        :param proto: `see socket.getaddrinfo()`
+        :param flags: `see socket.getaddrinfo()`
+        :param on_done: on_done(records|BaseException) callback for reporting
+            result from the given I/O loop. The single arg will be either an
+            exception object (check for `BaseException`) in case of failure or
+            the result returned by `socket.getaddrinfo()`.
+        """
+        check_callback_arg(on_done, 'on_done')
+
+        self._loop = native_loop
+        self._on_done = on_done
+        # Reference to the greenlet performing `getaddrinfo`.
+        self._greenlet = None
+        # getaddrinfo(..) args.
+        self._ga_host = host
+        self._ga_port = port
+        self._ga_family = family
+        self._ga_socktype = socktype
+        self._ga_proto = proto
+        self._ga_flags = flags
+
+    def start(self):
+        """Start an asynchronous getaddrinfo invocation."""
+        if self._greenlet is None:
+            self._greenlet = gevent.spawn_raw(self._resolve)
+        else:
+            LOGGER.warning("_GeventAddressResolver already started")
+
+    def cancel(self):
+        """Cancel the pending resolver."""
+        changed = False
+
+        if self._greenlet is not None:
+            changed = True
+            self._stop_greenlet()
+
+        self._cleanup()
+        return changed
+
+    def _cleanup(self):
+        """Stop the resolver and release any resources."""
+        self._stop_greenlet()
+        self._loop = None
+        self._on_done = None
+
+    def _stop_greenlet(self):
+        """Stop the greenlet performing getaddrinfo if running.
+
+        Otherwise, this is a no-op.
+        """
+        if self._greenlet is not None:
+            gevent.kill(self._greenlet)
+            self._greenlet = None
+
+    def _resolve(self):
+        """Call `getaddrinfo()` and return result via user's callback
+        function on the configured IO loop.
+        """
+        try:
+            # NOTE(JG): Can't use kwargs with getaddrinfo on Python <= v2.7.
+            result = gevent.socket.getaddrinfo(self._ga_host, self._ga_port,
+                                               self._ga_family,
+                                               self._ga_socktype,
+                                               self._ga_proto, self._ga_flags)
+        except Exception as exc:  # pylint: disable=broad-except
+            LOGGER.error('Address resolution failed: %r', exc)
+            result = exc
+
+        callback = functools.partial(self._dispatch_callback, result)
+        self._loop.add_callback(callback)
+
+    def _dispatch_callback(self, result):
+        """Invoke the configured completion callback and any subsequent cleanup.
+
+        :param result: result from getaddrinfo, or the exception if raised.
+        """
+        try:
+            LOGGER.debug(
+                'Invoking async getaddrinfo() completion callback; host=%r',
+                self._ga_host)
+            self._on_done(result)
+        finally:
+            self._cleanup()

backend/venv/Lib/site-packages/pika/adapters/tornado_connection.py

@@ -0,0 +1,90 @@
+"""Use pika with the Tornado IOLoop
+
+"""
+import logging
+
+from tornado import ioloop
+
+from pika.adapters.utils import nbio_interface, selector_ioloop_adapter
+from pika.adapters import base_connection
+
+LOGGER = logging.getLogger(__name__)
+
+
+class TornadoConnection(base_connection.BaseConnection):
+    """The TornadoConnection runs on the Tornado IOLoop.
+    """
+
+    def __init__(self,
+                 parameters=None,
+                 on_open_callback=None,
+                 on_open_error_callback=None,
+                 on_close_callback=None,
+                 custom_ioloop=None,
+                 internal_connection_workflow=True):
+        """Create a new instance of the TornadoConnection class, connecting
+        to RabbitMQ automatically.
+
+        :param pika.connection.Parameters|None parameters: The connection
+            parameters
+        :param callable|None on_open_callback: The method to call when the
+            connection is open
+        :param callable|None on_open_error_callback: Called if the connection
+            can't be established or connection establishment is interrupted by
+            `Connection.close()`:
+            on_open_error_callback(Connection, exception)
+        :param callable|None on_close_callback: Called when a previously fully
+            open connection is closed:
+            `on_close_callback(Connection, exception)`, where `exception` is
+            either an instance of `exceptions.ConnectionClosed` if closed by
+            user or broker or exception of another type that describes the
+            cause of connection failure
+        :param ioloop.IOLoop|nbio_interface.AbstractIOServices|None custom_ioloop:
+            Override using the global IOLoop in Tornado
+        :param bool internal_connection_workflow: True for autonomous connection
+            establishment which is default; False for externally-managed
+            connection workflow via the `create_connection()` factory
+
+        """
+        if isinstance(custom_ioloop, nbio_interface.AbstractIOServices):
+            nbio = custom_ioloop
+        else:
+            nbio = (selector_ioloop_adapter.SelectorIOServicesAdapter(
+                custom_ioloop or ioloop.IOLoop.instance()))
+        super(TornadoConnection, self).__init__(
+            parameters,
+            on_open_callback,
+            on_open_error_callback,
+            on_close_callback,
+            nbio,
+            internal_connection_workflow=internal_connection_workflow)
+
+    @classmethod
+    def create_connection(cls,
+                          connection_configs,
+                          on_done,
+                          custom_ioloop=None,
+                          workflow=None):
+        """Implement
+        :py:classmethod::`pika.adapters.BaseConnection.create_connection()`.
+
+        """
+        nbio = selector_ioloop_adapter.SelectorIOServicesAdapter(
+            custom_ioloop or ioloop.IOLoop.instance())
+
+        def connection_factory(params):
+            """Connection factory."""
+            if params is None:
+                raise ValueError('Expected pika.connection.Parameters '
+                                 'instance, but got None in params arg.')
+            return cls(
+                parameters=params,
+                custom_ioloop=nbio,
+                internal_connection_workflow=False)
+
+        return cls._start_connection_workflow(
+            connection_configs=connection_configs,
+            connection_factory=connection_factory,
+            nbio=nbio,
+            workflow=workflow,
+            on_done=on_done)

backend/venv/Lib/site-packages/pika/adapters/utils/connection_workflow.py

@@ -0,0 +1,866 @@
+"""Implements `AMQPConnectionWorkflow` - the default workflow of performing
+multiple TCP/[SSL]/AMQP connection attempts with timeouts and retries until one
+succeeds or all attempts fail.
+
+Defines the interface `AbstractAMQPConnectionWorkflow` that facilitates
+implementing custom connection workflows.
+
+"""
+
+import functools
+import logging
+import socket
+
+import pika.compat
+import pika.exceptions
+import pika.tcp_socket_opts
+from pika import __version__
+
+_LOG = logging.getLogger(__name__)
+
+
+class AMQPConnectorException(Exception):
+    """Base exception for this module"""
+
+
+class AMQPConnectorStackTimeout(AMQPConnectorException):
+    """Overall TCP/[SSL]/AMQP stack connection attempt timed out."""
+
+
+class AMQPConnectorAborted(AMQPConnectorException):
+    """Asynchronous request was aborted"""
+
+
+class AMQPConnectorWrongState(AMQPConnectorException):
+    """AMQPConnector operation requested in wrong state, such as aborting after
+    completion was reported.
+    """
+
+
+class AMQPConnectorPhaseErrorBase(AMQPConnectorException):
+    """Wrapper for exception that occurred during a particular bring-up phase.
+
+    """
+
+    def __init__(self, exception, *args):
+        """
+
+        :param BaseException exception: error that occurred while waiting for a
+            subclass-specific protocol bring-up phase to complete.
+        :param args: args for parent class
+        """
+        super(AMQPConnectorPhaseErrorBase, self).__init__(*args)
+        self.exception = exception
+
+    def __repr__(self):
+        return '{}: {!r}'.format(self.__class__.__name__, self.exception)
+
+
+class AMQPConnectorSocketConnectError(AMQPConnectorPhaseErrorBase):
+    """Error connecting TCP socket to remote peer"""
+
+
+class AMQPConnectorTransportSetupError(AMQPConnectorPhaseErrorBase):
+    """Error setting up transport after TCP connected but before AMQP handshake.
+
+    """
+
+
+class AMQPConnectorAMQPHandshakeError(AMQPConnectorPhaseErrorBase):
+    """Error during AMQP handshake"""
+
+
+class AMQPConnectionWorkflowAborted(AMQPConnectorException):
+    """AMQP Connection workflow was aborted."""
+
+
+class AMQPConnectionWorkflowWrongState(AMQPConnectorException):
+    """AMQP Connection Workflow operation requested in wrong state, such as
+    aborting after completion was reported.
+    """
+
+
+class AMQPConnectionWorkflowFailed(AMQPConnectorException):
+    """Indicates that AMQP connection workflow failed.
+
+    """
+
+    def __init__(self, exceptions, *args):
+        """
+        :param sequence exceptions: Exceptions that occurred during the
+            workflow.
+        :param args: args to pass to base class
+
+        """
+        super(AMQPConnectionWorkflowFailed, self).__init__(*args)
+        self.exceptions = tuple(exceptions)
+
+    def __repr__(self):
+        return ('{}: {} exceptions in all; last exception - {!r}; first '
+                'exception - {!r}').format(
+                    self.__class__.__name__, len(self.exceptions),
+                    self.exceptions[-1],
+                    self.exceptions[0] if len(self.exceptions) > 1 else None)
+
+
+class AMQPConnector(object):
+    """Performs a single TCP/[SSL]/AMQP connection workflow.
+
+    """
+
+    _STATE_INIT = 0  # start() hasn't been called yet
+    _STATE_TCP = 1  # TCP/IP connection establishment
+    _STATE_TRANSPORT = 2  # [SSL] and transport linkup
+    _STATE_AMQP = 3  # AMQP connection handshake
+    _STATE_TIMEOUT = 4  # overall TCP/[SSL]/AMQP timeout
+    _STATE_ABORTING = 5  # abort() called - aborting workflow
+    _STATE_DONE = 6  # result reported to client
+
+    def __init__(self, conn_factory, nbio):
+        """
+
+        :param callable conn_factory: A function that takes
+            `pika.connection.Parameters` as its only arg and returns a brand new
+            `pika.connection.Connection`-based adapter instance each time it is
+            called. The factory must instantiate the connection with
+            `internal_connection_workflow=False`.
+        :param pika.adapters.utils.nbio_interface.AbstractIOServices nbio:
+
+        """
+        self._conn_factory = conn_factory
+        self._nbio = nbio
+        self._addr_record = None  # type: tuple
+        self._conn_params = None  # type: pika.connection.Parameters
+        self._on_done = None  # will be provided via start()
+        # TCP connection timeout
+        # pylint: disable=C0301
+        self._tcp_timeout_ref = None  # type: pika.adapters.utils.nbio_interface.AbstractTimerReference
+        # Overall TCP/[SSL]/AMQP timeout
+        self._stack_timeout_ref = None  # type: pika.adapters.utils.nbio_interface.AbstractTimerReference
+        # Current task
+        self._task_ref = None  # type: pika.adapters.utils.nbio_interface.AbstractIOReference
+        self._sock = None  # type: socket.socket
+        self._amqp_conn = None  # type: pika.connection.Connection
+
+        self._state = self._STATE_INIT
+
+    def start(self, addr_record, conn_params, on_done):
+        """Asynchronously perform a single TCP/[SSL]/AMQP connection attempt.
+
+        :param tuple addr_record: a single resolved address record compatible
+            with `socket.getaddrinfo()` format.
+        :param pika.connection.Parameters conn_params:
+        :param callable on_done: Function to call upon completion of the
+            workflow: `on_done(pika.connection.Connection | BaseException)`. If
+            exception, it's going to be one of the following:
+                `AMQPConnectorSocketConnectError`
+                `AMQPConnectorTransportSetupError`
+                `AMQPConnectorAMQPHandshakeError`
+                `AMQPConnectorAborted`
+
+        """
+        if self._state != self._STATE_INIT:
+            raise AMQPConnectorWrongState(
+                'Already in progress or finished; state={}'.format(self._state))
+
+        self._addr_record = addr_record
+        self._conn_params = conn_params
+        self._on_done = on_done
+
+        # Create socket and initiate TCP/IP connection
+        self._state = self._STATE_TCP
+        self._sock = socket.socket(*self._addr_record[:3])
+        self._sock.setsockopt(pika.compat.SOL_TCP, socket.TCP_NODELAY, 1)
+        pika.tcp_socket_opts.set_sock_opts(self._conn_params.tcp_options,
+                                           self._sock)
+        self._sock.setblocking(False)
+
+        addr = self._addr_record[4]
+        _LOG.info('Pika version %s connecting to %r', __version__, addr)
+        self._task_ref = self._nbio.connect_socket(
+            self._sock, addr, on_done=self._on_tcp_connection_done)
+
+        # Start socket connection timeout timer
+        self._tcp_timeout_ref = None
+        if self._conn_params.socket_timeout is not None:
+            self._tcp_timeout_ref = self._nbio.call_later(
+                self._conn_params.socket_timeout,
+                self._on_tcp_connection_timeout)
+
+        # Start overall TCP/[SSL]/AMQP stack connection timeout timer
+        self._stack_timeout_ref = None
+        if self._conn_params.stack_timeout is not None:
+            self._stack_timeout_ref = self._nbio.call_later(
+                self._conn_params.stack_timeout, self._on_overall_timeout)
+
+    def abort(self):
+        """Abort the workflow asynchronously. The completion callback will be
+        called with an instance of AMQPConnectorAborted.
+
+        NOTE: we can't cancel/close synchronously because aborting pika
+        Connection and its transport requires an asynchronous operation.
+
+        :raises AMQPConnectorWrongState: If called after completion has been
+            reported or the workflow not started yet.
+        """
+        if self._state == self._STATE_INIT:
+            raise AMQPConnectorWrongState('Cannot abort before starting.')
+
+        if self._state == self._STATE_DONE:
+            raise AMQPConnectorWrongState('Cannot abort after completion was reported')
+
+        self._state = self._STATE_ABORTING
+        self._deactivate()
+
+        _LOG.info(
+            'AMQPConnector: beginning client-initiated asynchronous '
+            'abort; %r/%s', self._conn_params.host, self._addr_record)
+
+        if self._amqp_conn is None:
+            _LOG.debug('AMQPConnector.abort(): no connection, so just '
+                       'scheduling completion report via I/O loop.')
+            self._nbio.add_callback_threadsafe(
+                functools.partial(self._report_completion_and_cleanup,
+                                  AMQPConnectorAborted()))
+        else:
+            if not self._amqp_conn.is_closing:
+                # Initiate close of AMQP connection and wait for asynchronous
+                # callback from the Connection instance before reporting
+                # completion to client
+                _LOG.debug('AMQPConnector.abort(): closing Connection.')
+                self._amqp_conn.close(
+                    320, 'Client-initiated abort of AMQP Connection Workflow.')
+            else:
+                # It's already closing, must be due to our timeout processing,
+                # so we'll just piggy back on the callback it registered
+                _LOG.debug('AMQPConnector.abort(): closing of Connection was '
+                           'already initiated.')
+                assert self._state == self._STATE_TIMEOUT, \
+                    ('Connection is closing, but not in TIMEOUT state; state={}'
+                     .format(self._state))
+
+    def _close(self):
+        """Cancel asynchronous tasks and clean up to assist garbage collection.
+
+        Transition to STATE_DONE.
+
+        """
+        self._deactivate()
+
+        if self._sock is not None:
+            self._sock.close()
+            self._sock = None
+
+        self._conn_factory = None
+        self._nbio = None
+        self._addr_record = None
+        self._on_done = None
+
+        self._state = self._STATE_DONE
+
+    def _deactivate(self):
+        """Cancel asynchronous tasks.
+
+        """
+        # NOTE: self._amqp_conn requires special handling as it doesn't support
+        # synchronous closing. We special-case it elsewhere in the code where
+        # needed.
+        assert self._amqp_conn is None, \
+            '_deactivate called with self._amqp_conn not None; state={}'.format(
+                self._state)
+
+        if self._tcp_timeout_ref is not None:
+            self._tcp_timeout_ref.cancel()
+            self._tcp_timeout_ref = None
+
+        if self._stack_timeout_ref is not None:
+            self._stack_timeout_ref.cancel()
+            self._stack_timeout_ref = None
+
+        if self._task_ref is not None:
+            self._task_ref.cancel()
+            self._task_ref = None
+
+    def _report_completion_and_cleanup(self, result):
+        """Clean up and invoke client's `on_done` callback.
+
+        :param pika.connection.Connection | BaseException result: value to pass
+            to user's `on_done` callback.
+        """
+        if isinstance(result, BaseException):
+            _LOG.error('AMQPConnector - reporting failure: %r', result)
+        else:
+            _LOG.info('AMQPConnector - reporting success: %r', result)
+
+        on_done = self._on_done
+        self._close()
+
+        on_done(result)
+
+    def _on_tcp_connection_timeout(self):
+        """Handle TCP connection timeout
+
+        Reports AMQPConnectorSocketConnectError with socket.timeout inside.
+
+        """
+        self._tcp_timeout_ref = None
+
+        error = AMQPConnectorSocketConnectError(
+            socket.timeout('TCP connection attempt timed out: {!r}/{}'.format(
+                self._conn_params.host, self._addr_record)))
+        self._report_completion_and_cleanup(error)
+
+    def _on_overall_timeout(self):
+        """Handle overall TCP/[SSL]/AMQP connection attempt timeout by reporting
+        `Timeout` error to the client.
+
+        Reports AMQPConnectorSocketConnectError if timeout occurred during
+            socket TCP connection attempt.
+        Reports AMQPConnectorTransportSetupError if timeout occurred during
+            tramsport [SSL] setup attempt.
+        Reports AMQPConnectorAMQPHandshakeError if timeout occurred during
+            AMQP handshake.
+
+        """
+        self._stack_timeout_ref = None
+
+        prev_state = self._state
+        self._state = self._STATE_TIMEOUT
+
+        if prev_state == self._STATE_AMQP:
+            msg = ('Timeout while setting up AMQP to {!r}/{}; ssl={}'.format(
+                self._conn_params.host, self._addr_record,
+                bool(self._conn_params.ssl_options)))
+            _LOG.error(msg)
+            # Initiate close of AMQP connection and wait for asynchronous
+            # callback from the Connection instance before reporting completion
+            # to client
+            assert not self._amqp_conn.is_open, \
+                'Unexpected open state of {!r}'.format(self._amqp_conn)
+            if not self._amqp_conn.is_closing:
+                self._amqp_conn.close(320, msg)
+            return
+
+        if prev_state == self._STATE_TCP:
+            error = AMQPConnectorSocketConnectError(
+                AMQPConnectorStackTimeout(
+                    'Timeout while connecting socket to {!r}/{}'.format(
+                        self._conn_params.host, self._addr_record)))
+        else:
+            assert prev_state == self._STATE_TRANSPORT
+            error = AMQPConnectorTransportSetupError(
+                AMQPConnectorStackTimeout(
+                    'Timeout while setting up transport to {!r}/{}; ssl={}'.
+                    format(self._conn_params.host, self._addr_record,
+                           bool(self._conn_params.ssl_options))))
+
+        self._report_completion_and_cleanup(error)
+
+    def _on_tcp_connection_done(self, exc):
+        """Handle completion of asynchronous socket connection attempt.
+
+        Reports AMQPConnectorSocketConnectError if TCP socket connection
+            failed.
+
+        :param None|BaseException exc: None on success; exception object on
+            failure
+
+        """
+        self._task_ref = None
+        if self._tcp_timeout_ref is not None:
+            self._tcp_timeout_ref.cancel()
+            self._tcp_timeout_ref = None
+
+        if exc is not None:
+            _LOG.error('TCP Connection attempt failed: %r; dest=%r', exc,
+                       self._addr_record)
+            self._report_completion_and_cleanup(
+                AMQPConnectorSocketConnectError(exc))
+            return
+
+        # We succeeded in making a TCP/IP connection to the server
+        _LOG.debug('TCP connection to broker established: %r.', self._sock)
+
+        # Now set up the transport
+        self._state = self._STATE_TRANSPORT
+
+        ssl_context = server_hostname = None
+        if self._conn_params.ssl_options is not None:
+            ssl_context = self._conn_params.ssl_options.context
+            server_hostname = self._conn_params.ssl_options.server_hostname
+            if server_hostname is None:
+                server_hostname = self._conn_params.host
+
+        self._task_ref = self._nbio.create_streaming_connection(
+            protocol_factory=functools.partial(self._conn_factory,
+                                               self._conn_params),
+            sock=self._sock,
+            ssl_context=ssl_context,
+            server_hostname=server_hostname,
+            on_done=self._on_transport_establishment_done)
+
+        self._sock = None  # create_streaming_connection() takes ownership
+
+    def _on_transport_establishment_done(self, result):
+        """Handle asynchronous completion of
+        `AbstractIOServices.create_streaming_connection()`
+
+        Reports AMQPConnectorTransportSetupError if transport ([SSL]) setup
+            failed.
+
+        :param sequence|BaseException result: On success, a two-tuple
+            (transport, protocol); on failure, exception instance.
+
+        """
+        self._task_ref = None
+
+        if isinstance(result, BaseException):
+            _LOG.error(
+                'Attempt to create the streaming transport failed: %r; '
+                '%r/%s; ssl=%s', result, self._conn_params.host,
+                self._addr_record, bool(self._conn_params.ssl_options))
+            self._report_completion_and_cleanup(
+                AMQPConnectorTransportSetupError(result))
+            return
+
+        # We succeeded in setting up the streaming transport!
+        # result is a two-tuple (transport, protocol)
+        _LOG.info('Streaming transport linked up: %r.', result)
+        _transport, self._amqp_conn = result
+
+        # AMQP handshake is in progress - initiated during transport link-up
+        self._state = self._STATE_AMQP
+        # We explicitly remove default handler because it raises an exception.
+        self._amqp_conn.add_on_open_error_callback(
+            self._on_amqp_handshake_done, remove_default=True)
+        self._amqp_conn.add_on_open_callback(self._on_amqp_handshake_done)
+
+    def _on_amqp_handshake_done(self, connection, error=None):
+        """Handle completion of AMQP connection handshake attempt.
+
+        NOTE: we handle two types of callbacks - success with just connection
+        arg as well as the open-error callback with connection and error
+
+        Reports AMQPConnectorAMQPHandshakeError if AMQP handshake failed.
+
+        :param pika.connection.Connection connection:
+        :param BaseException | None error: None on success, otherwise
+            failure
+
+        """
+        _LOG.debug(
+            'AMQPConnector: AMQP handshake attempt completed; state=%s; '
+            'error=%r; %r/%s', self._state, error, self._conn_params.host,
+            self._addr_record)
+
+        # Don't need it any more; and _deactivate() checks that it's None
+        self._amqp_conn = None
+
+        if self._state == self._STATE_ABORTING:
+            # Client-initiated abort takes precedence over timeout
+            result = AMQPConnectorAborted()
+        elif self._state == self._STATE_TIMEOUT:
+            result = AMQPConnectorAMQPHandshakeError(
+                AMQPConnectorStackTimeout(
+                    'Timeout during AMQP handshake{!r}/{}; ssl={}'.format(
+                        self._conn_params.host, self._addr_record,
+                        bool(self._conn_params.ssl_options))))
+        elif self._state == self._STATE_AMQP:
+            if error is None:
+                _LOG.debug(
+                    'AMQPConnector: AMQP connection established for %r/%s: %r',
+                    self._conn_params.host, self._addr_record, connection)
+                result = connection
+            else:
+                _LOG.debug(
+                    'AMQPConnector: AMQP connection handshake failed for '
+                    '%r/%s: %r', self._conn_params.host, self._addr_record,
+                    error)
+                result = AMQPConnectorAMQPHandshakeError(error)
+        else:
+            # We timed out or aborted and initiated closing of the connection,
+            # but this callback snuck in
+            _LOG.debug(
+                'AMQPConnector: Ignoring AMQP handshake completion '
+                'notification due to wrong state=%s; error=%r; conn=%r',
+                self._state, error, connection)
+            return
+
+        self._report_completion_and_cleanup(result)
+
+
+class AbstractAMQPConnectionWorkflow(pika.compat.AbstractBase):
+    """Interface for implementing a custom TCP/[SSL]/AMQP connection workflow.
+
+    """
+
+    def start(self, connection_configs, connector_factory, native_loop,
+              on_done):
+        """Asynchronously perform the workflow until success or all retries
+        are exhausted. Called by the adapter.
+
+        :param sequence connection_configs: A sequence of one or more
+            `pika.connection.Parameters`-based objects. Will attempt to connect
+            using each config in the given order.
+        :param callable connector_factory: call it without args to obtain a new
+            instance of `AMQPConnector` for each connection attempt.
+            See `AMQPConnector` for details.
+        :param native_loop: Native I/O loop passed by app to the adapter or
+            obtained by the adapter by default.
+        :param callable on_done: Function to call upon completion of the
+            workflow:
+            `on_done(pika.connection.Connection |
+                     AMQPConnectionWorkflowFailed |
+                     AMQPConnectionWorkflowAborted)`.
+            `Connection`-based adapter on success,
+            `AMQPConnectionWorkflowFailed` on failure,
+            `AMQPConnectionWorkflowAborted` if workflow was aborted.
+
+        :raises AMQPConnectionWorkflowWrongState: If called in wrong state, such
+            as after starting the workflow.
+        """
+        raise NotImplementedError
+
+    def abort(self):
+        """Abort the workflow asynchronously. The completion callback will be
+        called with an instance of AMQPConnectionWorkflowAborted.
+
+        NOTE: we can't cancel/close synchronously because aborting pika
+        Connection and its transport requires an asynchronous operation.
+
+        :raises AMQPConnectionWorkflowWrongState: If called in wrong state, such
+            as before starting or after completion has been reported.
+        """
+        raise NotImplementedError
+
+
+class AMQPConnectionWorkflow(AbstractAMQPConnectionWorkflow):
+    """Implements Pika's default workflow for performing multiple TCP/[SSL]/AMQP
+    connection attempts with timeouts and retries until one succeeds or all
+    attempts fail.
+
+    The workflow:
+        while not success and retries remain:
+            1. For each given config (pika.connection.Parameters object):
+                A. Perform DNS resolution of the config's host.
+                B. Attempt to establish TCP/[SSL]/AMQP for each resolved address
+                   until one succeeds, in which case we're done.
+            2. If all configs failed but retries remain, resume from beginning
+               after the given retry pause. NOTE: failure of DNS resolution
+               is equivalent to one cycle and will be retried after the pause
+               if retries remain.
+
+    """
+
+    _SOCK_TYPE = socket.SOCK_STREAM
+    _IPPROTO = socket.IPPROTO_TCP
+
+    _STATE_INIT = 0
+    _STATE_ACTIVE = 1
+    _STATE_ABORTING = 2
+    _STATE_DONE = 3
+
+    def __init__(self, _until_first_amqp_attempt=False):
+        """
+        :param int | float retry_pause: Non-negative number of seconds to wait
+            before retrying the config sequence. Meaningful only if retries is
+            greater than 0. Defaults to 2 seconds.
+        :param bool _until_first_amqp_attempt: INTERNAL USE ONLY; ends workflow
+            after first AMQP handshake attempt, regardless of outcome (success
+            or failure). The automatic connection logic in
+            `pika.connection.Connection` enables this because it's not
+            designed/tested to reset all state properly to handle more than one
+            AMQP handshake attempt.
+
+        TODO: Do we need getaddrinfo timeout?
+        TODO: Would it be useful to implement exponential back-off?
+
+        """
+        self._attempts_remaining = None  # supplied by start()
+        self._retry_pause = None  # supplied by start()
+        self._until_first_amqp_attempt = _until_first_amqp_attempt
+
+        # Provided by set_io_services()
+        # pylint: disable=C0301
+        self._nbio = None  # type: pika.adapters.utils.nbio_interface.AbstractIOServices
+
+        # Current index within `_connection_configs`; initialized when
+        # starting a new connection sequence.
+        self._current_config_index = None
+
+        self._connection_configs = None  # supplied by start()
+        self._connector_factory = None  # supplied by start()
+        self._on_done = None  # supplied by start()
+
+        self._connector = None  # type: AMQPConnector
+
+        self._task_ref = None  # current cancelable asynchronous task or timer
+        self._addrinfo_iter = None
+
+        # Exceptions from all failed connection attempts in this workflow
+        self._connection_errors = []
+
+        self._state = self._STATE_INIT
+
+    def set_io_services(self, nbio):
+        """Called by the conneciton adapter only on pika's
+        `AMQPConnectionWorkflow` instance to provide it the adapter-specific
+        `AbstractIOServices` object before calling the `start()` method.
+
+        NOTE: Custom workflow implementations should use the native I/O loop
+        directly because `AbstractIOServices` is private to Pika
+        implementation and its interface may change without notice.
+
+        :param pika.adapters.utils.nbio_interface.AbstractIOServices nbio:
+
+        """
+        self._nbio = nbio
+
+    def start(
+            self,
+            connection_configs,
+            connector_factory,
+            native_loop,  # pylint: disable=W0613
+            on_done):
+        """Override `AbstractAMQPConnectionWorkflow.start()`.
+
+        NOTE: This implementation uses `connection_attempts` and `retry_delay`
+        values from the last element of the given `connection_configs` sequence
+        as the overall number of connection attempts of the entire
+        `connection_configs` sequence and pause between each sequence.
+
+        """
+        if self._state != self._STATE_INIT:
+            raise AMQPConnectorWrongState(
+                'Already in progress or finished; state={}'.format(self._state))
+
+        try:
+            iter(connection_configs)
+        except Exception as error:
+            raise TypeError(
+                'connection_configs does not support iteration: {!r}'.format(
+                    error))
+        if not connection_configs:
+            raise ValueError(
+                'connection_configs is empty: {!r}.'.format(connection_configs))
+
+        self._connection_configs = connection_configs
+        self._connector_factory = connector_factory
+        self._on_done = on_done
+
+        self._attempts_remaining = connection_configs[-1].connection_attempts
+        self._retry_pause = connection_configs[-1].retry_delay
+
+        self._state = self._STATE_ACTIVE
+
+        _LOG.debug('Starting AMQP Connection workflow asynchronously.')
+
+        # Begin from our own I/O loop context to avoid calling back into client
+        # from client's call here
+        self._task_ref = self._nbio.call_later(
+            0, functools.partial(self._start_new_cycle_async, first=True))
+
+    def abort(self):
+        """Override `AbstractAMQPConnectionWorkflow.abort()`.
+
+        """
+        if self._state == self._STATE_INIT:
+            raise AMQPConnectorWrongState('Cannot abort before starting.')
+        elif self._state == self._STATE_DONE:
+            raise AMQPConnectorWrongState(
+                'Cannot abort after completion was reported')
+
+        self._state = self._STATE_ABORTING
+        self._deactivate()
+
+        _LOG.info('AMQPConnectionWorkflow: beginning client-initiated '
+                  'asynchronous abort.')
+
+        if self._connector is None:
+            _LOG.debug('AMQPConnectionWorkflow.abort(): no connector, so just '
+                       'scheduling completion report via I/O loop.')
+            self._nbio.add_callback_threadsafe(
+                functools.partial(self._report_completion_and_cleanup,
+                                  AMQPConnectionWorkflowAborted()))
+        else:
+            _LOG.debug('AMQPConnectionWorkflow.abort(): requesting '
+                       'connector.abort().')
+            self._connector.abort()
+
+    def _close(self):
+        """Cancel asynchronous tasks and clean up to assist garbage collection.
+
+        Transition to _STATE_DONE.
+
+        """
+        self._deactivate()
+
+        self._connection_configs = None
+        self._nbio = None
+        self._connector_factory = None
+        self._on_done = None
+        self._connector = None
+        self._addrinfo_iter = None
+        self._connection_errors = None
+
+        self._state = self._STATE_DONE
+
+    def _deactivate(self):
+        """Cancel asynchronous tasks.
+
+        """
+        if self._task_ref is not None:
+            self._task_ref.cancel()
+            self._task_ref = None
+
+    def _report_completion_and_cleanup(self, result):
+        """Clean up and invoke client's `on_done` callback.
+
+        :param pika.connection.Connection | AMQPConnectionWorkflowFailed result:
+            value to pass to user's `on_done` callback.
+        """
+        if isinstance(result, BaseException):
+            _LOG.error('AMQPConnectionWorkflow - reporting failure: %r', result)
+        else:
+            _LOG.info('AMQPConnectionWorkflow - reporting success: %r', result)
+
+        on_done = self._on_done
+        self._close()
+
+        on_done(result)
+
+    def _start_new_cycle_async(self, first):
+        """Start a new workflow cycle (if any more attempts are left) beginning
+        with the first Parameters object in self._connection_configs. If out of
+        attempts, report `AMQPConnectionWorkflowFailed`.
+
+        :param bool first: if True, don't delay; otherwise delay next attempt by
+            `self._retry_pause` seconds.
+        """
+        self._task_ref = None
+
+        assert self._attempts_remaining >= 0, self._attempts_remaining
+
+        if self._attempts_remaining <= 0:
+            error = AMQPConnectionWorkflowFailed(self._connection_errors)
+            _LOG.error('AMQP connection workflow failed: %r.', error)
+            self._report_completion_and_cleanup(error)
+            return
+
+        self._attempts_remaining -= 1
+        _LOG.debug(
+            'Beginning a new AMQP connection workflow cycle; attempts '
+            'remaining after this: %s', self._attempts_remaining)
+
+        self._current_config_index = None
+
+        self._task_ref = self._nbio.call_later(
+            0 if first else self._retry_pause, self._try_next_config_async)
+
+    def _try_next_config_async(self):
+        """Attempt to connect using the next Parameters config. If there are no
+        more configs, start a new cycle.
+
+        """
+        self._task_ref = None
+
+        if self._current_config_index is None:
+            self._current_config_index = 0
+        else:
+            self._current_config_index += 1
+
+        if self._current_config_index >= len(self._connection_configs):
+            _LOG.debug('_try_next_config_async: starting a new cycle.')
+            self._start_new_cycle_async(first=False)
+            return
+
+        params = self._connection_configs[self._current_config_index]
+
+        _LOG.debug('_try_next_config_async: %r:%s', params.host, params.port)
+
+        # Begin with host address resolution
+        assert self._task_ref is None
+        self._task_ref = self._nbio.getaddrinfo(
+            host=params.host,
+            port=params.port,
+            socktype=self._SOCK_TYPE,
+            proto=self._IPPROTO,
+            on_done=self._on_getaddrinfo_async_done)
+
+    def _on_getaddrinfo_async_done(self, addrinfos_or_exc):
+        """Handles completion callback from asynchronous `getaddrinfo()`.
+
+        :param list | BaseException addrinfos_or_exc: resolved address records
+            returned by `getaddrinfo()` or an exception object from failure.
+        """
+        self._task_ref = None
+
+        if isinstance(addrinfos_or_exc, BaseException):
+            _LOG.error('getaddrinfo failed: %r.', addrinfos_or_exc)
+            self._connection_errors.append(addrinfos_or_exc)
+            self._start_new_cycle_async(first=False)
+            return
+
+        _LOG.debug('getaddrinfo returned %s records', len(addrinfos_or_exc))
+        self._addrinfo_iter = iter(addrinfos_or_exc)
+
+        self._try_next_resolved_address()
+
+    def _try_next_resolved_address(self):
+        """Try connecting using next resolved address. If there aren't any left,
+        continue with next Parameters config.
+
+        """
+        try:
+            addr_record = next(self._addrinfo_iter)
+        except StopIteration:
+            _LOG.debug(
+                '_try_next_resolved_address: continuing with next config.')
+            self._try_next_config_async()
+            return
+
+        _LOG.debug('Attempting to connect using address record %r', addr_record)
+
+        self._connector = self._connector_factory()  # type: AMQPConnector
+
+        self._connector.start(
+            addr_record=addr_record,
+            conn_params=self._connection_configs[self._current_config_index],
+            on_done=self._on_connector_done)
+
+    def _on_connector_done(self, conn_or_exc):
+        """Handle completion of connection attempt by `AMQPConnector`.
+
+        :param pika.connection.Connection | BaseException conn_or_exc: See
+            `AMQPConnector.start()` for exception details.
+
+        """
+        self._connector = None
+        _LOG.debug('Connection attempt completed with %r', conn_or_exc)
+
+        if isinstance(conn_or_exc, BaseException):
+            self._connection_errors.append(conn_or_exc)
+
+            if isinstance(conn_or_exc, AMQPConnectorAborted):
+                assert self._state == self._STATE_ABORTING, \
+                    'Expected _STATE_ABORTING, but got {!r}'.format(self._state)
+
+                self._report_completion_and_cleanup(
+                    AMQPConnectionWorkflowAborted())
+            elif (self._until_first_amqp_attempt and
+                  isinstance(conn_or_exc, AMQPConnectorAMQPHandshakeError)):
+                _LOG.debug('Ending AMQP connection workflow after first failed '
+                           'AMQP handshake due to _until_first_amqp_attempt.')
+                if isinstance(conn_or_exc.exception,
+                              pika.exceptions.ConnectionOpenAborted):
+                    error = AMQPConnectionWorkflowAborted
+                else:
+                    error = AMQPConnectionWorkflowFailed(
+                        self._connection_errors)
+
+                self._report_completion_and_cleanup(error)
+            else:
+                self._try_next_resolved_address()
+        else:
+            # Success!
+            self._report_completion_and_cleanup(conn_or_exc)

backend/venv/Lib/site-packages/pika/adapters/utils/nbio_interface.py

@@ -0,0 +1,441 @@
+"""Non-blocking I/O interface for pika connection adapters.
+
+I/O interface expected by `pika.adapters.base_connection.BaseConnection`
+
+NOTE: This API is modeled after asyncio in python3 for a couple of reasons
+    1. It's a sensible API
+    2. To make it easy to implement at least on top of the built-in asyncio
+
+Furthermore, the API caters to the needs of pika core and lack of generalization
+is intentional for the sake of reducing complexity of the implementation and
+testing and lessening the maintenance burden.
+
+"""
+import abc
+
+import pika.compat
+
+
+class AbstractIOServices(pika.compat.AbstractBase):
+    """Interface to I/O services required by `pika.adapters.BaseConnection` and
+    related utilities.
+
+    NOTE: This is not a public API. Pika users should rely on the native I/O
+    loop APIs (e.g., asyncio event loop, tornado ioloop, twisted reactor, etc.)
+    that corresponds to the chosen Connection adapter.
+
+    """
+
+    @abc.abstractmethod
+    def get_native_ioloop(self):
+        """Returns the native I/O loop instance, such as Twisted reactor,
+        asyncio's or tornado's event loop
+
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def close(self):
+        """Release IOLoop's resources.
+
+        the `close()` method is intended to be called by Pika's own test
+        code only after `start()` returns. After calling `close()`, no other
+        interaction with the closed instance of `IOLoop` should be performed.
+
+        NOTE: This method is provided for Pika's own test scripts that need to
+        be able to run I/O loops generically to test multiple Connection Adapter
+        implementations. Pika users should use the native I/O loop's API
+        instead.
+
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def run(self):
+        """Run the I/O loop. It will loop until requested to exit. See `stop()`.
+
+        NOTE: the outcome or restarting an instance that had been stopped is
+        UNDEFINED!
+
+        NOTE: This method is provided for Pika's own test scripts that need to
+        be able to run I/O loops generically to test multiple Connection Adapter
+        implementations (not all of the supported I/O Loop frameworks have
+        methods named start/stop). Pika users should use the native I/O loop's
+        API instead.
+
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def stop(self):
+        """Request exit from the ioloop. The loop is NOT guaranteed to
+        stop before this method returns.
+
+        NOTE: The outcome of calling `stop()` on a non-running instance is
+        UNDEFINED!
+
+        NOTE: This method is provided for Pika's own test scripts that need to
+        be able to run I/O loops generically to test multiple Connection Adapter
+        implementations (not all of the supported I/O Loop frameworks have
+        methods named start/stop). Pika users should use the native I/O loop's
+        API instead.
+
+        To invoke `stop()` safely from a thread other than this IOLoop's thread,
+        call it via `add_callback_threadsafe`; e.g.,
+
+            `ioloop.add_callback_threadsafe(ioloop.stop)`
+
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def add_callback_threadsafe(self, callback):
+        """Requests a call to the given function as soon as possible. It will be
+        called from this IOLoop's thread.
+
+        NOTE: This is the only thread-safe method offered by the IOLoop adapter.
+              All other manipulations of the IOLoop adapter and objects governed
+              by it must be performed from the IOLoop's thread.
+
+        NOTE: if you know that the requester is running on the same thread as
+              the connection it is more efficient to use the
+              `ioloop.call_later()` method with a delay of 0.
+
+        :param callable callback: The callback method; must be callable.
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def call_later(self, delay, callback):
+        """Add the callback to the IOLoop timer to be called after delay seconds
+        from the time of call on best-effort basis. Returns a handle to the
+        timeout.
+
+        If two are scheduled for the same time, it's undefined which one will
+        be called first.
+
+        :param float delay: The number of seconds to wait to call callback
+        :param callable callback: The callback method
+        :returns: A handle that can be used to cancel the request.
+        :rtype: AbstractTimerReference
+
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def getaddrinfo(self,
+                    host,
+                    port,
+                    on_done,
+                    family=0,
+                    socktype=0,
+                    proto=0,
+                    flags=0):
+        """Perform the equivalent of `socket.getaddrinfo()` asynchronously.
+
+        See `socket.getaddrinfo()` for the standard args.
+
+        :param callable on_done: user callback that takes the return value of
+            `socket.getaddrinfo()` upon successful completion or exception upon
+            failure (check for `BaseException`) as its only arg. It will not be
+            called if the operation was cancelled.
+        :rtype: AbstractIOReference
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def connect_socket(self, sock, resolved_addr, on_done):
+        """Perform the equivalent of `socket.connect()` on a previously-resolved
+        address asynchronously.
+
+        IMPLEMENTATION NOTE: Pika's connection logic resolves the addresses
+            prior to making socket connections, so we don't need to burden the
+            implementations of this method with the extra logic of asynchronous
+            DNS resolution. Implementations can use `socket.inet_pton()` to
+            verify the address.
+
+        :param socket.socket sock: non-blocking socket that needs to be
+            connected via `socket.socket.connect()`
+        :param tuple resolved_addr: resolved destination address/port two-tuple
+            as per `socket.socket.connect()`, except that the first element must
+            be an actual IP address that's consistent with the given socket's
+            address family.
+        :param callable on_done: user callback that takes None upon successful
+            completion or exception (check for `BaseException`) upon error as
+            its only arg. It will not be called if the operation was cancelled.
+
+        :rtype: AbstractIOReference
+        :raises ValueError: if host portion of `resolved_addr` is not an IP
+            address or is inconsistent with the socket's address family as
+            validated via `socket.inet_pton()`
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def create_streaming_connection(self,
+                                    protocol_factory,
+                                    sock,
+                                    on_done,
+                                    ssl_context=None,
+                                    server_hostname=None):
+        """Perform SSL session establishment, if requested, on the already-
+        connected socket and link the streaming transport/protocol pair.
+
+        NOTE: This method takes ownership of the socket.
+
+        :param callable protocol_factory: called without args, returns an
+            instance with the `AbstractStreamProtocol` interface. The protocol's
+            `connection_made(transport)` method will be called to link it to
+            the transport after remaining connection activity (e.g., SSL session
+            establishment), if any, is completed successfully.
+        :param socket.socket sock: Already-connected, non-blocking
+            `socket.SOCK_STREAM` socket to be used by the transport. We take
+            ownership of this socket.
+        :param callable on_done: User callback
+            `on_done(BaseException | (transport, protocol))` to be notified when
+            the asynchronous operation completes. An exception arg indicates
+            failure (check for `BaseException`); otherwise the two-tuple will
+            contain the linked transport/protocol pair having
+            AbstractStreamTransport and AbstractStreamProtocol interfaces
+            respectively.
+        :param None | ssl.SSLContext ssl_context: if None, this will proceed as
+            a plaintext connection; otherwise, if not None, SSL session
+            establishment will be performed prior to linking the transport and
+            protocol.
+        :param str | None server_hostname: For use during SSL session
+            establishment to match against the target server's certificate. The
+            value `None` disables this check (which is a huge security risk)
+        :rtype: AbstractIOReference
+        """
+        raise NotImplementedError
+
+
+class AbstractFileDescriptorServices(pika.compat.AbstractBase):
+    """Interface definition of common non-blocking file descriptor services
+    required by some utility implementations.
+
+    NOTE: This is not a public API. Pika users should rely on the native I/O
+    loop APIs (e.g., asyncio event loop, tornado ioloop, twisted reactor, etc.)
+    that corresponds to the chosen Connection adapter.
+
+    """
+
+    @abc.abstractmethod
+    def set_reader(self, fd, on_readable):
+        """Call the given callback when the file descriptor is readable.
+        Replace prior reader, if any, for the given file descriptor.
+
+        :param fd: file descriptor
+        :param callable on_readable: a callback taking no args to be notified
+            when fd becomes readable.
+
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def remove_reader(self, fd):
+        """Stop watching the given file descriptor for readability
+
+        :param fd: file descriptor
+        :returns: True if reader was removed; False if none was registered.
+        :rtype: bool
+
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def set_writer(self, fd, on_writable):
+        """Call the given callback whenever the file descriptor is writable.
+        Replace prior writer callback, if any, for the given file descriptor.
+
+        IMPLEMENTATION NOTE: For portability, implementations of
+            `set_writable()` should also watch for indication of error on the
+            socket and treat it as equivalent to the writable indication (e.g.,
+            also adding the socket to the `exceptfds` arg of `socket.select()`
+            and calling the `on_writable` callback if `select.select()`
+            indicates that the socket is in error state). Specifically, Windows
+            (unlike POSIX) only indicates error on the socket (but not writable)
+            when connection establishment fails.
+
+        :param fd: file descriptor
+        :param callable on_writable: a callback taking no args to be notified
+            when fd becomes writable.
+
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def remove_writer(self, fd):
+        """Stop watching the given file descriptor for writability
+
+        :param fd: file descriptor
+        :returns: True if reader was removed; False if none was registered.
+        :rtype: bool
+
+        """
+        raise NotImplementedError
+
+
+class AbstractTimerReference(pika.compat.AbstractBase):
+    """Reference to asynchronous operation"""
+
+    @abc.abstractmethod
+    def cancel(self):
+        """Cancel callback. If already cancelled, has no affect.
+        """
+        raise NotImplementedError
+
+
+class AbstractIOReference(pika.compat.AbstractBase):
+    """Reference to asynchronous I/O operation"""
+
+    @abc.abstractmethod
+    def cancel(self):
+        """Cancel pending operation
+
+        :returns: False if was already done or cancelled; True otherwise
+        :rtype: bool
+        """
+        raise NotImplementedError
+
+
+class AbstractStreamProtocol(pika.compat.AbstractBase):
+    """Stream protocol interface. It's compatible with a subset of
+    `asyncio.protocols.Protocol` for compatibility with asyncio-based
+    `AbstractIOServices` implementation.
+
+    """
+
+    @abc.abstractmethod
+    def connection_made(self, transport):
+        """Introduces transport to protocol after transport is connected.
+
+        :param AbstractStreamTransport transport:
+        :raises Exception: Exception-based exception on error
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def connection_lost(self, error):
+        """Called upon loss or closing of connection.
+
+        NOTE: `connection_made()` and `connection_lost()` are each called just
+        once and in that order. All other callbacks are called between them.
+
+        :param BaseException | None error: An exception (check for
+            `BaseException`) indicates connection failure. None indicates that
+            connection was closed on this side, such as when it's aborted or
+            when `AbstractStreamProtocol.eof_received()` returns a result that
+            doesn't evaluate to True.
+        :raises Exception: Exception-based exception on error
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def eof_received(self):
+        """Called after the remote peer shuts its write end of the connection.
+
+        :returns: A falsy value (including None) will cause the transport to
+            close itself, resulting in an eventual `connection_lost()` call
+            from the transport. If a truthy value is returned, it will be the
+            protocol's responsibility to close/abort the transport.
+        :rtype: falsy|truthy
+        :raises Exception: Exception-based exception on error
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def data_received(self, data):
+        """Called to deliver incoming data to the protocol.
+
+        :param data: Non-empty data bytes.
+        :raises Exception: Exception-based exception on error
+        """
+        raise NotImplementedError
+
+    # pylint: disable=W0511
+    # TODO Undecided whether we need write flow-control yet, although it seems
+    #      like a good idea.
+    # @abc.abstractmethod
+    # def pause_writing(self):
+    #     """Called when the transport's write buffer size becomes greater than or
+    #     equal to the transport's high-water mark. It won't be called again until
+    #     the transport's write buffer gets back to its low-water mark and then
+    #     returns to/past the hight-water mark again.
+    #     """
+    #     raise NotImplementedError
+    #
+    # @abc.abstractmethod
+    # def resume_writing(self):
+    #     """Called when the transport's write buffer size becomes less than or
+    #     equal to the transport's low-water mark.
+    #     """
+    #     raise NotImplementedError
+
+
+class AbstractStreamTransport(pika.compat.AbstractBase):
+    """Stream transport interface. It's compatible with a subset of
+    `asyncio.transports.Transport` for compatibility with asyncio-based
+    `AbstractIOServices` implementation.
+
+    """
+
+    @abc.abstractmethod
+    def abort(self):
+        """Close connection abruptly without waiting for pending I/O to
+        complete. Will invoke the corresponding protocol's `connection_lost()`
+        method asynchronously (not in context of the abort() call).
+
+        :raises Exception: Exception-based exception on error
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def get_protocol(self):
+        """Return the protocol linked to this transport.
+
+        :rtype: AbstractStreamProtocol
+        :raises Exception: Exception-based exception on error
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def write(self, data):
+        """Buffer the given data until it can be sent asynchronously.
+
+        :param bytes data:
+        :raises ValueError: if called with empty data
+        :raises Exception: Exception-based exception on error
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def get_write_buffer_size(self):
+        """
+        :returns: Current size of output data buffered by the transport
+        :rtype: int
+        """
+        raise NotImplementedError
+
+    # pylint: disable=W0511
+    # TODO Udecided whether we need write flow-control yet, although it seems
+    #      like a good idea.
+    # @abc.abstractmethod
+    # def set_write_buffer_limits(self, high, low):
+    #     """Set thresholds for calling the protocol's `pause_writing()`
+    #     and `resume_writing()` methods. `low` must be less than or equal to
+    #     `high`.
+    #
+    #     NOTE The unintuitive order of the args is preserved to match the
+    #     corresponding method in `asyncio.WriteTransport`. I would expect `low`
+    #     to be the first arg, especially since
+    #     `asyncio.WriteTransport.get_write_buffer_limits()` returns them in the
+    #     opposite order. This seems error-prone.
+    #
+    #     See `asyncio.WriteTransport.get_write_buffer_limits()` for more details
+    #     about the args.
+    #
+    #     :param int high: non-negative high-water mark.
+    #     :param int low: non-negative low-water mark.
+    #     """
+    #     raise NotImplementedError

backend/venv/Lib/site-packages/pika/adapters/utils/selector_ioloop_adapter.py

@@ -0,0 +1,600 @@
+"""
+Implementation of `nbio_interface.AbstractIOServices` on top of a
+selector-based I/O loop, such as tornado's and our home-grown
+select_connection's I/O loops.
+
+"""
+import abc
+import logging
+import socket
+import threading
+
+from pika.adapters.utils import nbio_interface, io_services_utils
+from pika.adapters.utils.io_services_utils import (check_callback_arg,
+                                                   check_fd_arg)
+
+LOGGER = logging.getLogger(__name__)
+
+
+class AbstractSelectorIOLoop(object):
+    """Selector-based I/O loop interface expected by
+    `selector_ioloop_adapter.SelectorIOServicesAdapter`
+
+    NOTE: this interface follows the corresponding methods and attributes
+     of `tornado.ioloop.IOLoop` in order to avoid additional adapter layering
+     when wrapping tornado's IOLoop.
+    """
+
+    @property
+    @abc.abstractmethod
+    def READ(self):  # pylint: disable=C0103
+        """The value of the I/O loop's READ flag; READ/WRITE/ERROR may be used
+        with bitwise operators as expected.
+
+        Implementation note: the implementations can simply replace these
+        READ/WRITE/ERROR properties with class-level attributes
+
+        """
+
+    @property
+    @abc.abstractmethod
+    def WRITE(self):  # pylint: disable=C0103
+        """The value of the I/O loop's WRITE flag; READ/WRITE/ERROR may be used
+        with bitwise operators as expected
+
+        """
+
+    @property
+    @abc.abstractmethod
+    def ERROR(self):  # pylint: disable=C0103
+        """The value of the I/O loop's ERROR flag; READ/WRITE/ERROR may be used
+        with bitwise operators as expected
+
+        """
+
+    @abc.abstractmethod
+    def close(self):
+        """Release IOLoop's resources.
+
+        the `close()` method is intended to be called by the application or test
+        code only after `start()` returns. After calling `close()`, no other
+        interaction with the closed instance of `IOLoop` should be performed.
+
+        """
+
+    @abc.abstractmethod
+    def start(self):
+        """Run the I/O loop. It will loop until requested to exit. See `stop()`.
+
+        """
+
+    @abc.abstractmethod
+    def stop(self):
+        """Request exit from the ioloop. The loop is NOT guaranteed to
+        stop before this method returns.
+
+        To invoke `stop()` safely from a thread other than this IOLoop's thread,
+        call it via `add_callback_threadsafe`; e.g.,
+
+            `ioloop.add_callback(ioloop.stop)`
+
+        """
+
+    @abc.abstractmethod
+    def call_later(self, delay, callback):
+        """Add the callback to the IOLoop timer to be called after delay seconds
+        from the time of call on best-effort basis. Returns a handle to the
+        timeout.
+
+        :param float delay: The number of seconds to wait to call callback
+        :param callable callback: The callback method
+        :returns: handle to the created timeout that may be passed to
+            `remove_timeout()`
+        :rtype: object
+
+        """
+
+    @abc.abstractmethod
+    def remove_timeout(self, timeout_handle):
+        """Remove a timeout
+
+        :param timeout_handle: Handle of timeout to remove
+
+        """
+
+    @abc.abstractmethod
+    def add_callback(self, callback):
+        """Requests a call to the given function as soon as possible in the
+        context of this IOLoop's thread.
+
+        NOTE: This is the only thread-safe method in IOLoop. All other
+        manipulations of IOLoop must be performed from the IOLoop's thread.
+
+        For example, a thread may request a call to the `stop` method of an
+        ioloop that is running in a different thread via
+        `ioloop.add_callback_threadsafe(ioloop.stop)`
+
+        :param callable callback: The callback method
+
+        """
+
+    @abc.abstractmethod
+    def add_handler(self, fd, handler, events):
+        """Start watching the given file descriptor for events
+
+        :param int fd: The file descriptor
+        :param callable handler: When requested event(s) occur,
+            `handler(fd, events)` will be called.
+        :param int events: The event mask using READ, WRITE, ERROR.
+
+        """
+
+    @abc.abstractmethod
+    def update_handler(self, fd, events):
+        """Changes the events we watch for
+
+        :param int fd: The file descriptor
+        :param int events: The event mask using READ, WRITE, ERROR
+
+        """
+
+    @abc.abstractmethod
+    def remove_handler(self, fd):
+        """Stop watching the given file descriptor for events
+
+        :param int fd: The file descriptor
+
+        """
+
+
+class SelectorIOServicesAdapter(io_services_utils.SocketConnectionMixin,
+                                io_services_utils.StreamingConnectionMixin,
+                                nbio_interface.AbstractIOServices,
+                                nbio_interface.AbstractFileDescriptorServices):
+    """Implements the
+    :py:class:`.nbio_interface.AbstractIOServices` interface
+    on top of selector-style native loop having the
+    :py:class:`AbstractSelectorIOLoop` interface, such as
+    :py:class:`pika.selection_connection.IOLoop` and :py:class:`tornado.IOLoop`.
+
+    NOTE:
+    :py:class:`.nbio_interface.AbstractFileDescriptorServices`
+    interface is only required by the mixins.
+
+    """
+
+    def __init__(self, native_loop):
+        """
+        :param AbstractSelectorIOLoop native_loop: An instance compatible with
+            the `AbstractSelectorIOLoop` interface, but not necessarily derived
+            from it.
+        """
+        self._loop = native_loop
+
+        # Active watchers: maps file descriptors to `_FileDescriptorCallbacks`
+        self._watchers = dict()
+
+        # Native loop-specific event masks of interest
+        self._readable_mask = self._loop.READ
+        # NOTE: tying ERROR to WRITE is particularly handy for Windows, whose
+        # `select.select()` differs from Posix by reporting
+        # connection-establishment failure only through exceptfds (ERROR event),
+        # while the typical application workflow is to wait for the socket to
+        # become writable when waiting for socket connection to be established.
+        self._writable_mask = self._loop.WRITE | self._loop.ERROR
+
+    def get_native_ioloop(self):
+        """Implement
+        :py:meth:`.nbio_interface.AbstractIOServices.get_native_ioloop()`.
+
+        """
+        return self._loop
+
+    def close(self):
+        """Implement :py:meth:`.nbio_interface.AbstractIOServices.close()`.
+
+        """
+        self._loop.close()
+
+    def run(self):
+        """Implement :py:meth:`.nbio_interface.AbstractIOServices.run()`.
+
+        """
+        self._loop.start()
+
+    def stop(self):
+        """Implement :py:meth:`.nbio_interface.AbstractIOServices.stop()`.
+
+        """
+        self._loop.stop()
+
+    def add_callback_threadsafe(self, callback):
+        """Implement
+        :py:meth:`.nbio_interface.AbstractIOServices.add_callback_threadsafe()`.
+
+        """
+        self._loop.add_callback(callback)
+
+    def call_later(self, delay, callback):
+        """Implement :py:meth:`.nbio_interface.AbstractIOServices.call_later()`.
+
+        """
+        return _TimerHandle(self._loop.call_later(delay, callback), self._loop)
+
+    def getaddrinfo(self,
+                    host,
+                    port,
+                    on_done,
+                    family=0,
+                    socktype=0,
+                    proto=0,
+                    flags=0):
+        """Implement :py:meth:`.nbio_interface.AbstractIOServices.getaddrinfo()`.
+
+        """
+        return _SelectorIOLoopIOHandle(
+            _AddressResolver(
+                native_loop=self._loop,
+                host=host,
+                port=port,
+                family=family,
+                socktype=socktype,
+                proto=proto,
+                flags=flags,
+                on_done=on_done).start())
+
+    def set_reader(self, fd, on_readable):
+        """Implement
+        :py:meth:`.nbio_interface.AbstractFileDescriptorServices.set_reader()`.
+
+        """
+        LOGGER.debug('SelectorIOServicesAdapter.set_reader(%s, %r)', fd,
+                     on_readable)
+
+        check_fd_arg(fd)
+        check_callback_arg(on_readable, 'on_readable')
+
+        try:
+            callbacks = self._watchers[fd]
+        except KeyError:
+            self._loop.add_handler(fd, self._on_reader_writer_fd_events,
+                                   self._readable_mask)
+            self._watchers[fd] = _FileDescriptorCallbacks(reader=on_readable)
+            LOGGER.debug('set_reader(%s, _) added handler Rd', fd)
+        else:
+            if callbacks.reader is None:
+                assert callbacks.writer is not None
+                self._loop.update_handler(
+                    fd, self._readable_mask | self._writable_mask)
+                LOGGER.debug('set_reader(%s, _) updated handler RdWr', fd)
+            else:
+                LOGGER.debug('set_reader(%s, _) replacing reader', fd)
+
+            callbacks.reader = on_readable
+
+    def remove_reader(self, fd):
+        """Implement
+        :py:meth:`.nbio_interface.AbstractFileDescriptorServices.remove_reader()`.
+
+        """
+        LOGGER.debug('SelectorIOServicesAdapter.remove_reader(%s)', fd)
+
+        check_fd_arg(fd)
+
+        try:
+            callbacks = self._watchers[fd]
+        except KeyError:
+            LOGGER.debug('remove_reader(%s) neither was set', fd)
+            return False
+
+        if callbacks.reader is None:
+            assert callbacks.writer is not None
+            LOGGER.debug('remove_reader(%s) reader wasn\'t set Wr', fd)
+            return False
+
+        callbacks.reader = None
+
+        if callbacks.writer is None:
+            del self._watchers[fd]
+            self._loop.remove_handler(fd)
+            LOGGER.debug('remove_reader(%s) removed handler', fd)
+        else:
+            self._loop.update_handler(fd, self._writable_mask)
+            LOGGER.debug('remove_reader(%s) updated handler Wr', fd)
+
+        return True
+
+    def set_writer(self, fd, on_writable):
+        """Implement
+        :py:meth:`.nbio_interface.AbstractFileDescriptorServices.set_writer()`.
+
+        """
+        LOGGER.debug('SelectorIOServicesAdapter.set_writer(%s, %r)', fd,
+                     on_writable)
+
+        check_fd_arg(fd)
+        check_callback_arg(on_writable, 'on_writable')
+
+        try:
+            callbacks = self._watchers[fd]
+        except KeyError:
+            self._loop.add_handler(fd, self._on_reader_writer_fd_events,
+                                   self._writable_mask)
+            self._watchers[fd] = _FileDescriptorCallbacks(writer=on_writable)
+            LOGGER.debug('set_writer(%s, _) added handler Wr', fd)
+        else:
+            if callbacks.writer is None:
+                assert callbacks.reader is not None
+                # NOTE: Set the writer func before setting the mask!
+                # Otherwise a race condition can occur where ioloop tries to
+                # call writer when it is still None.
+                callbacks.writer = on_writable
+                self._loop.update_handler(
+                    fd, self._readable_mask | self._writable_mask)
+                LOGGER.debug('set_writer(%s, _) updated handler RdWr', fd)
+            else:
+                LOGGER.debug('set_writer(%s, _) replacing writer', fd)
+                callbacks.writer = on_writable
+
+    def remove_writer(self, fd):
+        """Implement
+        :py:meth:`.nbio_interface.AbstractFileDescriptorServices.remove_writer()`.
+
+        """
+        LOGGER.debug('SelectorIOServicesAdapter.remove_writer(%s)', fd)
+
+        check_fd_arg(fd)
+
+        try:
+            callbacks = self._watchers[fd]
+        except KeyError:
+            LOGGER.debug('remove_writer(%s) neither was set.', fd)
+            return False
+
+        if callbacks.writer is None:
+            assert callbacks.reader is not None
+            LOGGER.debug('remove_writer(%s) writer wasn\'t set Rd', fd)
+            return False
+
+        callbacks.writer = None
+
+        if callbacks.reader is None:
+            del self._watchers[fd]
+            self._loop.remove_handler(fd)
+            LOGGER.debug('remove_writer(%s) removed handler', fd)
+        else:
+            self._loop.update_handler(fd, self._readable_mask)
+            LOGGER.debug('remove_writer(%s) updated handler Rd', fd)
+
+        return True
+
+    def _on_reader_writer_fd_events(self, fd, events):
+        """Handle indicated file descriptor events requested via `set_reader()`
+        and `set_writer()`.
+
+        :param fd: file descriptor
+        :param events: event mask using native loop's READ/WRITE/ERROR. NOTE:
+            depending on the underlying poller mechanism, ERROR may be indicated
+            upon certain file description state even though we don't request it.
+            We ignore ERROR here since `set_reader()`/`set_writer()` don't
+            request for it.
+        """
+        callbacks = self._watchers[fd]
+
+        if events & self._readable_mask and callbacks.reader is None:
+            # NOTE: we check for consistency here ahead of the writer callback
+            # because the writer callback, if any, can change the events being
+            # watched
+            LOGGER.warning(
+                'READ indicated on fd=%s, but reader callback is None; '
+                'events=%s', fd, bin(events))
+
+        if events & self._writable_mask:
+            if callbacks.writer is not None:
+                callbacks.writer()
+            else:
+                LOGGER.warning(
+                    'WRITE indicated on fd=%s, but writer callback is None; '
+                    'events=%s', fd, bin(events))
+
+        if events & self._readable_mask:
+            if callbacks.reader is not None:
+                callbacks.reader()
+            else:
+                # Reader callback might have been removed in the scope of writer
+                # callback.
+                pass
+
+
+class _FileDescriptorCallbacks(object):
+    """Holds reader and writer callbacks for a file descriptor"""
+
+    __slots__ = ('reader', 'writer')
+
+    def __init__(self, reader=None, writer=None):
+
+        self.reader = reader
+        self.writer = writer
+
+
+class _TimerHandle(nbio_interface.AbstractTimerReference):
+    """This module's adaptation of `nbio_interface.AbstractTimerReference`.
+
+    """
+
+    def __init__(self, handle, loop):
+        """
+
+        :param opaque handle: timer handle from the underlying loop
+            implementation that may be passed to its `remove_timeout()` method
+        :param AbstractSelectorIOLoop loop: the I/O loop instance that created
+            the timeout.
+        """
+        self._handle = handle
+        self._loop = loop
+
+    def cancel(self):
+        if self._loop is not None:
+            self._loop.remove_timeout(self._handle)
+            self._handle = None
+            self._loop = None
+
+
+class _SelectorIOLoopIOHandle(nbio_interface.AbstractIOReference):
+    """This module's adaptation of `nbio_interface.AbstractIOReference`
+
+    """
+
+    def __init__(self, subject):
+        """
+        :param subject: subject of the reference containing a `cancel()` method
+
+        """
+        self._cancel = subject.cancel
+
+    def cancel(self):
+        """Cancel pending operation
+
+        :returns: False if was already done or cancelled; True otherwise
+        :rtype: bool
+
+        """
+        return self._cancel()
+
+
+class _AddressResolver(object):
+    """Performs getaddrinfo asynchronously using a thread, then reports result
+    via callback from the given I/O loop.
+
+    NOTE: at this stage, we're using a thread per request, which may prove
+    inefficient and even prohibitive if the app performs many of these
+    operations concurrently.
+    """
+    NOT_STARTED = 0
+    ACTIVE = 1
+    CANCELED = 2
+    COMPLETED = 3
+
+    def __init__(self, native_loop, host, port, family, socktype, proto, flags,
+                 on_done):
+        """
+
+        :param AbstractSelectorIOLoop native_loop:
+        :param host: `see socket.getaddrinfo()`
+        :param port: `see socket.getaddrinfo()`
+        :param family: `see socket.getaddrinfo()`
+        :param socktype: `see socket.getaddrinfo()`
+        :param proto: `see socket.getaddrinfo()`
+        :param flags: `see socket.getaddrinfo()`
+        :param on_done: on_done(records|BaseException) callback for reporting
+            result from the given I/O loop. The single arg will be either an
+            exception object (check for `BaseException`) in case of failure or
+            the result returned by `socket.getaddrinfo()`.
+        """
+        check_callback_arg(on_done, 'on_done')
+
+        self._state = self.NOT_STARTED
+        self._result = None
+        self._loop = native_loop
+        self._host = host
+        self._port = port
+        self._family = family
+        self._socktype = socktype
+        self._proto = proto
+        self._flags = flags
+        self._on_done = on_done
+
+        self._mutex = threading.Lock()
+        self._threading_timer = None
+
+    def _cleanup(self):
+        """Release resources
+
+        """
+        self._loop = None
+        self._threading_timer = None
+        self._on_done = None
+
+    def start(self):
+        """Start asynchronous DNS lookup.
+
+        :rtype: nbio_interface.AbstractIOReference
+
+        """
+        assert self._state == self.NOT_STARTED, self._state
+
+        self._state = self.ACTIVE
+        self._threading_timer = threading.Timer(0, self._resolve)
+        self._threading_timer.start()
+
+        return _SelectorIOLoopIOHandle(self)
+
+    def cancel(self):
+        """Cancel the pending resolver
+
+        :returns: False if was already done or cancelled; True otherwise
+        :rtype: bool
+
+        """
+        # Try to cancel, but no guarantees
+        with self._mutex:
+            if self._state == self.ACTIVE:
+                LOGGER.debug('Canceling resolver for %s:%s', self._host,
+                             self._port)
+                self._state = self.CANCELED
+
+                # Attempt to cancel, but not guaranteed
+                self._threading_timer.cancel()
+
+                self._cleanup()
+
+                return True
+            else:
+                LOGGER.debug(
+                    'Ignoring _AddressResolver cancel request when not ACTIVE; '
+                    '(%s:%s); state=%s', self._host, self._port, self._state)
+                return False
+
+    def _resolve(self):
+        """Call `socket.getaddrinfo()` and return result via user's callback
+        function on the given I/O loop
+
+        """
+        try:
+            # NOTE: on python 2.x, can't pass keyword args to getaddrinfo()
+            result = socket.getaddrinfo(self._host, self._port, self._family,
+                                        self._socktype, self._proto,
+                                        self._flags)
+        except Exception as exc:  # pylint: disable=W0703
+            LOGGER.error('Address resolution failed: %r', exc)
+            result = exc
+
+        self._result = result
+
+        # Schedule result to be returned to user via user's event loop
+        with self._mutex:
+            if self._state == self.ACTIVE:
+                self._loop.add_callback(self._dispatch_result)
+            else:
+                LOGGER.debug(
+                    'Asynchronous getaddrinfo cancellation detected; '
+                    'in thread; host=%r', self._host)
+
+    def _dispatch_result(self):
+        """This is called from the user's I/O loop to pass the result to the
+         user via the user's on_done callback
+
+        """
+        if self._state == self.ACTIVE:
+            self._state = self.COMPLETED
+            try:
+                LOGGER.debug(
+                    'Invoking asynchronous getaddrinfo() completion callback; '
+                    'host=%r', self._host)
+                self._on_done(self._result)
+            finally:
+                self._cleanup()
+        else:
+            LOGGER.debug(
+                'Asynchronous getaddrinfo cancellation detected; '
+                'in I/O loop context; host=%r', self._host)